diff --git a/src/components/InputArray.tsx b/src/components/InputArray.tsx
index 0d2a79c3a..5864e904f 100644
--- a/src/components/InputArray.tsx
+++ b/src/components/InputArray.tsx
@@ -3,17 +3,17 @@ import InputString from './InputString'
 import InputNumber from './InputNumber'
 
 export type FieldArrayProps = {
-  value: string[] | number[]
+  value: (string | number | undefined)[]
   type?: string
   length?: number
-  default?: string[] | number[]
-  onChange?(...args: unknown[]): unknown
+  default?: (string | number | undefined)[]
+  onChange?(value: (string | number | undefined)[] | undefined): unknown
   'aria-label'?: string
   label?: string
 };
 
 type FieldArrayState = {
-  value: string[] | number[]
+  value: (string | number | undefined)[]
   initialPropsValue: unknown[]
 }
 
@@ -59,7 +59,7 @@ export default class FieldArray extends React.Component<FieldArrayProps, FieldAr
     });
   }
 
-  changeValue(idx: number, newValue: string) {
+  changeValue(idx: number, newValue: string | number | undefined) {
     const value = this.state.value.slice(0);
     value[idx] = newValue;
 
@@ -93,7 +93,7 @@ export default class FieldArray extends React.Component<FieldArrayProps, FieldAr
           default={containsValues || !this.props.default ? undefined : this.props.default[i] as number}
           value={value[i] as number}
           required={containsValues ? true : false}
-          onChange={this.changeValue.bind(this, i)}
+          onChange={(v) => this.changeValue(i, v)}
           aria-label={this.props['aria-label'] || this.props.label}
         />
       } else {
diff --git a/src/components/InputDynamicArray.tsx b/src/components/InputDynamicArray.tsx
index 4de4ab181..1e6d77c58 100644
--- a/src/components/InputDynamicArray.tsx
+++ b/src/components/InputDynamicArray.tsx
@@ -11,10 +11,10 @@ import InputUrl from './InputUrl'
 
 
 export type FieldDynamicArrayProps = {
-  value?: (string | number)[]
+  value?: (string | number | undefined)[]
   type?: 'url' | 'number' | 'enum' | 'string'
-  default?: (string | number)[]
-  onChange?(...args: unknown[]): unknown
+  default?: (string | number | undefined)[]
+  onChange?(values: (string | number | undefined)[] | undefined): unknown
   style?: object
   fieldSpec?: {
     values?: any
@@ -25,7 +25,7 @@ export type FieldDynamicArrayProps = {
 
 
 export default class FieldDynamicArray extends React.Component<FieldDynamicArrayProps> {
-  changeValue(idx: number, newValue: string | number) {
+  changeValue(idx: number, newValue: string | number | undefined) {
     const values = this.values.slice(0)
     values[idx] = newValue
     if (this.props.onChange) this.props.onChange(values)
diff --git a/src/components/InputNumber.tsx b/src/components/InputNumber.tsx
index eb7d6e182..85631a119 100644
--- a/src/components/InputNumber.tsx
+++ b/src/components/InputNumber.tsx
@@ -7,7 +7,7 @@ export type InputNumberProps = {
   default?: number
   min?: number
   max?: number
-  onChange?(...args: unknown[]): unknown
+  onChange?(value: number | undefined): unknown
   allowRange?: boolean
   rangeStep?: number
   wdKey?: string
diff --git a/src/components/InputSelect.tsx b/src/components/InputSelect.tsx
index 9a8f94856..53b627f3a 100644
--- a/src/components/InputSelect.tsx
+++ b/src/components/InputSelect.tsx
@@ -5,7 +5,7 @@ export type InputSelectProps = {
   "data-wd-key"?: string
   options: [string, any][] | string[]
   style?: object
-  onChange(...args: unknown[]): unknown
+  onChange(value: string): unknown
   title?: string
   'aria-label'?: string
 };
diff --git a/src/components/InputSpec.tsx b/src/components/InputSpec.tsx
index 0100f1e85..f989faca3 100644
--- a/src/components/InputSpec.tsx
+++ b/src/components/InputSpec.tsx
@@ -14,11 +14,11 @@ import capitalize from 'lodash.capitalize'
 const iconProperties = ['background-pattern', 'fill-pattern', 'line-pattern', 'fill-extrusion-pattern', 'icon-image']
 
 export type SpecFieldProps = {
-  onChange?(...args: unknown[]): unknown
+  onChange?(fieldName: string | undefined, value: number | undefined | (string | number | undefined)[]): unknown
   fieldName?: string
-  fieldSpec: {
+  fieldSpec?: {
     default?: unknown
-    type: 'number' | 'enum' | 'resolvedImage' | 'formatted' | 'string' | 'color' | 'boolean' | 'array'
+    type?: 'number' | 'enum' | 'resolvedImage' | 'formatted' | 'string' | 'color' | 'boolean' | 'array'
     minimum?: number
     maximum?: number
     values?: unknown[]
@@ -29,9 +29,9 @@ export type SpecFieldProps = {
   /** Override the style of the field */
   style?: object
   'aria-label'?: string
-  error: unknown[]
-  label: string
-  action: ReactElement
+  error?: unknown[]
+  label?: string
+  action?: ReactElement
 };
 
 /** Display any field from the Maplibre GL style spec and
@@ -47,12 +47,12 @@ export default class SpecField extends React.Component<SpecFieldProps> {
       action: this.props.action,
       style: this.props.style,
       value: this.props.value,
-      default: this.props.fieldSpec.default,
+      default: this.props.fieldSpec?.default,
       name: this.props.fieldName,
-      onChange: (newValue: string) => this.props.onChange!(this.props.fieldName, newValue),
+      onChange: (newValue: number | undefined | (string | number | undefined)[]) => this.props.onChange!(this.props.fieldName, newValue),
       'aria-label': this.props['aria-label'],
     }
-    switch(this.props.fieldSpec.type) {
+    switch(this.props.fieldSpec?.type) {
       case 'number': return (
         <InputNumber
           {...commonProps as InputNumberProps}
diff --git a/src/components/InputString.tsx b/src/components/InputString.tsx
index ee1d0bc6e..d301485ad 100644
--- a/src/components/InputString.tsx
+++ b/src/components/InputString.tsx
@@ -5,8 +5,8 @@ export type InputStringProps = {
   value?: string
   style?: object
   default?: string
-  onChange?(...args: unknown[]): unknown
-  onInput?(...args: unknown[]): unknown
+  onChange?(value: string | undefined): unknown
+  onInput?(value: string | undefined): unknown
   multi?: boolean
   required?: boolean
   disabled?: boolean
diff --git a/src/components/ModalSources.tsx b/src/components/ModalSources.tsx
index aad35cf4f..9669b08ef 100644
--- a/src/components/ModalSources.tsx
+++ b/src/components/ModalSources.tsx
@@ -233,7 +233,7 @@ class AddSource extends React.Component<AddSourceProps, AddSourceState> {
           ['image', 'Image'],
           ['video', 'Video'],
         ]}
-        onChange={(mode: EditorMode) => this.setState({mode: mode, source: this.defaultSource(mode)})}
+        onChange={mode => this.setState({mode: mode as EditorMode, source: this.defaultSource(mode as EditorMode)})}
         value={this.state.mode as string}
       />
       <ModalSourcesTypeEditor
diff --git a/src/components/SpecField.tsx b/src/components/SpecField.tsx
index 650c70c88..a2cb47ebf 100644
--- a/src/components/SpecField.tsx
+++ b/src/components/SpecField.tsx
@@ -21,9 +21,9 @@ type SpecFieldProps = InputFieldSpecProps & {
 
 export default class SpecField extends React.Component<SpecFieldProps> {
   render() {
-    const fieldType = this.props.fieldSpec.type;
+    const fieldType = this.props.fieldSpec?.type;
 
-    const typeBlockFn = typeMap[fieldType];
+    const typeBlockFn = typeMap[fieldType!];
 
     let TypeBlock;
     if (typeBlockFn) {
diff --git a/src/components/_DataProperty.jsx b/src/components/_DataProperty.tsx
similarity index 74%
rename from src/components/_DataProperty.jsx
rename to src/components/_DataProperty.tsx
index ac203dd13..948a28aeb 100644
--- a/src/components/_DataProperty.jsx
+++ b/src/components/_DataProperty.tsx
@@ -1,5 +1,4 @@
 import React from 'react'
-import PropTypes from 'prop-types'
 import {mdiFunctionVariant, mdiTableRowPlusAfter} from '@mdi/js';
 import {latest} from '@maplibre/maplibre-gl-style-spec'
 
@@ -8,7 +7,6 @@ import InputSpec from './InputSpec'
 import InputNumber from './InputNumber'
 import InputString from './InputString'
 import InputSelect from './InputSelect'
-import FieldDocLabel from './FieldDocLabel'
 import Block from './Block'
 import docUid from '../libs/document-uid'
 import sortNumerically from '../libs/sort-numerically'
@@ -19,12 +17,12 @@ import DeleteStopButton from './_DeleteStopButton'
 
 
 
-function setStopRefs(props, state) {
+function setStopRefs(props: DataPropertyProps, state: DataPropertyState) {
   // This is initialsed below only if required to improved performance.
-  let newRefs;
+  let newRefs: {[key: number]: string} | undefined;
 
   if(props.value && props.value.stops) {
-    props.value.stops.forEach((val, idx) => {
+    props.value.stops.forEach((_val, idx) => {
       if(!state.refs.hasOwnProperty(idx)) {
         if(!newRefs) {
           newRefs = {...state};
@@ -37,27 +35,39 @@ function setStopRefs(props, state) {
   return newRefs;
 }
 
-export default class DataProperty extends React.Component {
-  static propTypes = {
-    onChange: PropTypes.func,
-    onDeleteStop: PropTypes.func,
-    onAddStop: PropTypes.func,
-    onExpressionClick: PropTypes.func,
-    fieldName: PropTypes.string,
-    fieldType: PropTypes.string,
-    fieldSpec: PropTypes.object,
-    value: PropTypes.oneOfType([
-      PropTypes.object,
-      PropTypes.string,
-      PropTypes.number,
-      PropTypes.bool,
-      PropTypes.array
-    ]),
-    errors: PropTypes.object,
-  }
+type DataPropertyProps = {
+  onChange?(fieldName: string, value: any): unknown
+  onDeleteStop?(...args: unknown[]): unknown
+  onAddStop?(...args: unknown[]): unknown
+  onExpressionClick?(...args: unknown[]): unknown
+  onChangeToZoomFunction?(...args: unknown[]): unknown
+  fieldName: string
+  fieldType?: string
+  fieldSpec?: object
+  value?: DataPropertyValue
+  errors?: object
+};
+
+type DataPropertyState = {
+  refs: {[key: number]: string}
+};
+
+type DataPropertyValue = {
+  default?: any
+  property?: string
+  base?: number
+  type?: string
+  stops: Stops
+}
+
+type Stops = [{
+  zoom: number
+  value: number
+}, number][]
 
+export default class DataProperty extends React.Component<DataPropertyProps, DataPropertyState> {
   state = {
-    refs: {}
+    refs: {} as {[key: number]: string}
   }
 
   componentDidMount() {
@@ -70,7 +80,7 @@ export default class DataProperty extends React.Component {
     }
   }
 
-  static getDerivedStateFromProps(props, state) {
+  static getDerivedStateFromProps(props: DataPropertyProps, state: DataPropertyState) {
     const newRefs = setStopRefs(props, state);
     if(newRefs) {
       return {
@@ -80,7 +90,7 @@ export default class DataProperty extends React.Component {
     return null;
   }
 
-  getFieldFunctionType(fieldSpec) {
+  getFieldFunctionType(fieldSpec: any) {
     if (fieldSpec.expression.interpolated) {
       return "exponential"
     }
@@ -90,7 +100,7 @@ export default class DataProperty extends React.Component {
     return "categorical"
   }
 
-  getDataFunctionTypes(fieldSpec) {
+  getDataFunctionTypes(fieldSpec: any) {
     if (fieldSpec.expression.interpolated) {
       return ["interpolate", "categorical", "interval", "exponential", "identity"]
     }
@@ -100,7 +110,7 @@ export default class DataProperty extends React.Component {
   }
 
   // Order the stops altering the refs to reflect their new position.
-  orderStopsByZoom(stops) {
+  orderStopsByZoom(stops: Stops) {
     const mappedWithRef = stops
       .map((stop, idx) => {
         return {
@@ -112,7 +122,7 @@ export default class DataProperty extends React.Component {
       .sort((a, b) => sortNumerically(a.data[0].zoom, b.data[0].zoom));
 
     // Fetch the new position of the stops
-    const newRefs = {};
+    const newRefs = {} as {[key: number]: string};
     mappedWithRef
       .forEach((stop, idx) =>{
         newRefs[idx] = stop.ref;
@@ -125,7 +135,7 @@ export default class DataProperty extends React.Component {
     return mappedWithRef.map((item) => item.data);
   }
 
-  onChange = (fieldName, value) => {
+  onChange = (fieldName: string, value: any) => {
     if (value.type === "identity") {
       value = {
         type: value.type,
@@ -139,21 +149,21 @@ export default class DataProperty extends React.Component {
         type: value.type,
         // Default props if they don't already exist.
         stops: [
-          [{zoom: 6, value: stopValue}, findDefaultFromSpec(this.props.fieldSpec)],
-          [{zoom: 10, value: stopValue}, findDefaultFromSpec(this.props.fieldSpec)]
+          [{zoom: 6, value: stopValue}, findDefaultFromSpec(this.props.fieldSpec as any)],
+          [{zoom: 10, value: stopValue}, findDefaultFromSpec(this.props.fieldSpec as any)]
         ],
         ...value,
       }
     }
-    this.props.onChange(fieldName, value);
+    this.props.onChange!(fieldName, value);
   }
 
-  changeStop(changeIdx, stopData, value) {
-    const stops = this.props.value.stops.slice(0)
+  changeStop(changeIdx: number, stopData: { zoom: number | undefined, value: number }, value: number) {
+    const stops = this.props.value?.stops.slice(0) || []
     // const changedStop = stopData.zoom === undefined ? stopData.value : stopData
     stops[changeIdx] = [
       {
-        ...stopData,
+        value: stopData.value,
         zoom: (stopData.zoom === undefined) ? 0 : stopData.zoom,
       },
       value
@@ -168,7 +178,7 @@ export default class DataProperty extends React.Component {
     this.onChange(this.props.fieldName, changedValue)
   }
 
-  changeBase(newValue) {
+  changeBase(newValue: number | undefined) {
     const changedValue = {
       ...this.props.value,
       base: newValue
@@ -177,11 +187,11 @@ export default class DataProperty extends React.Component {
     if (changedValue.base === undefined) {
       delete changedValue["base"];
     }
-    this.props.onChange(this.props.fieldName, changedValue)
+    this.props.onChange!(this.props.fieldName, changedValue)
   }
 
-  changeDataType(propVal) {
-    if (propVal === "interpolate") {
+  changeDataType(propVal: string) {
+    if (propVal === "interpolate" && this.props.onChangeToZoomFunction) {
       this.props.onChangeToZoomFunction();
     }
     else {
@@ -192,41 +202,39 @@ export default class DataProperty extends React.Component {
     }
   }
 
-  changeDataProperty(propName, propVal) {
+  changeDataProperty(propName: "property" | "default", propVal: any) {
     if (propVal) {
-      this.props.value[propName] = propVal
+      this.props.value![propName] = propVal
     }
     else {
-      delete this.props.value[propName]
+      delete this.props.value![propName]
     }
     this.onChange(this.props.fieldName, this.props.value)
   }
 
   render() {
-    const {fieldName, fieldType, errors} = this.props;
-
-    if (typeof this.props.value.type === "undefined") {
-      this.props.value.type = this.getFieldFunctionType(this.props.fieldSpec)
+    if (typeof this.props.value?.type === "undefined") {
+      this.props.value!.type = this.getFieldFunctionType(this.props.fieldSpec)
     }
 
     let dataFields;
-    if (this.props.value.stops) {
+    if (this.props.value?.stops) {
       dataFields = this.props.value.stops.map((stop, idx) => {
         const zoomLevel = typeof stop[0] === 'object' ? stop[0].zoom : undefined;
         const key  = this.state.refs[idx];
         const dataLevel = typeof stop[0] === 'object' ? stop[0].value : stop[0];
         const value = stop[1]
-        const deleteStopBtn = <DeleteStopButton onClick={this.props.onDeleteStop.bind(this, idx)} />
+        const deleteStopBtn = <DeleteStopButton onClick={this.props.onDeleteStop?.bind(this, idx)} />
 
         const dataProps = {
           'aria-label': "Input value",
           label: "Data value",
-          value: dataLevel,
-          onChange: newData => this.changeStop(idx, { zoom: zoomLevel, value: newData }, value)
+          value: dataLevel as any,
+          onChange: (newData: string | number | undefined) => this.changeStop(idx, { zoom: zoomLevel, value: newData as number }, value)
         }
 
         let dataInput;
-        if(this.props.value.type === "categorical") {
+        if(this.props.value?.type === "categorical") {
           dataInput = <InputString {...dataProps} />
         }
         else {
@@ -246,16 +254,6 @@ export default class DataProperty extends React.Component {
           </div>
         }
 
-        const errorKeyStart = `${fieldType}.${fieldName}.stops[${idx}]`;
-        const foundErrors = Object.entries(errors).filter(([key, error]) => {
-          return key.startsWith(errorKeyStart);
-        });
-
-        const message = foundErrors.map(([key, error]) => {
-          return error.message;
-        }).join("");
-        const error = message ? {message} : undefined;
-
         return <tr key={key}>
           <td>
             {zoomInput}
@@ -269,7 +267,7 @@ export default class DataProperty extends React.Component {
               fieldName={this.props.fieldName}
               fieldSpec={this.props.fieldSpec}
               value={value}
-              onChange={(_, newValue) => this.changeStop(idx, {zoom: zoomLevel, value: dataLevel}, newValue)}
+              onChange={(_, newValue) => this.changeStop(idx, {zoom: zoomLevel, value: dataLevel}, newValue as number)}
             />
           </td>
           <td>
@@ -289,14 +287,14 @@ export default class DataProperty extends React.Component {
           >
             <div className="maputnik-data-spec-property-input">
               <InputSelect
-                value={this.props.value.type}
+                value={this.props.value!.type}
                 onChange={propVal => this.changeDataType(propVal)}
                 title={"Select a type of data scale (default is 'categorical')."}
                 options={this.getDataFunctionTypes(this.props.fieldSpec)}
               />
             </div>
           </Block>
-          {this.props.value.type !== "identity" &&
+          {this.props.value?.type !== "identity" &&
             <Block
               label={"Base"}
               key="base"
@@ -305,8 +303,8 @@ export default class DataProperty extends React.Component {
                 <InputSpec
                   fieldName={"base"}
                   fieldSpec={latest.function.base}
-                  value={this.props.value.base}
-                  onChange={(_, newValue) => this.changeBase(newValue)}
+                  value={this.props.value?.base}
+                  onChange={(_, newValue) => this.changeBase(newValue as number)}
                 />
               </div>
             </Block>
@@ -317,8 +315,7 @@ export default class DataProperty extends React.Component {
           >
             <div className="maputnik-data-spec-property-input">
               <InputString
-                value={this.props.value.property}
-                title={"Input a data property to base styles off of."}
+                value={this.props.value?.property}
                 onChange={propVal => this.changeDataProperty("property", propVal)}
               />
             </div>
@@ -331,7 +328,7 @@ export default class DataProperty extends React.Component {
               <InputSpec
                 fieldName={this.props.fieldName}
                 fieldSpec={this.props.fieldSpec}
-                value={this.props.value.default}
+                value={this.props.value?.default}
                 onChange={(_, propVal) => this.changeDataProperty("default", propVal)}
               />
             </Block>
@@ -344,7 +341,7 @@ export default class DataProperty extends React.Component {
                   <tr>
                     <th>Zoom</th>
                     <th>Input value</th>
-                    <th rowSpan="2">Output value</th>
+                    <th rowSpan={2}>Output value</th>
                   </tr>
                 </thead>
                 <tbody>
@@ -357,7 +354,7 @@ export default class DataProperty extends React.Component {
             {dataFields &&
               <InputButton
                 className="maputnik-add-stop"
-                onClick={this.props.onAddStop.bind(this)}
+                onClick={this.props.onAddStop?.bind(this)}
               >
                 <svg style={{width:"14px", height:"14px", verticalAlign: "text-bottom"}} viewBox="0 0 24 24">
                   <path fill="currentColor" d={mdiTableRowPlusAfter} />
@@ -366,7 +363,7 @@ export default class DataProperty extends React.Component {
             }
             <InputButton
               className="maputnik-add-stop"
-              onClick={this.props.onExpressionClick.bind(this)}
+              onClick={this.props.onExpressionClick?.bind(this)}
             >
               <svg style={{width:"14px", height:"14px", verticalAlign: "text-bottom"}} viewBox="0 0 24 24">
                 <path fill="currentColor" d={mdiFunctionVariant} />
diff --git a/src/components/_ExpressionProperty.jsx b/src/components/_ExpressionProperty.tsx
similarity index 75%
rename from src/components/_ExpressionProperty.jsx
rename to src/components/_ExpressionProperty.tsx
index 09bdfda77..fbafdcfd2 100644
--- a/src/components/_ExpressionProperty.jsx
+++ b/src/components/_ExpressionProperty.tsx
@@ -1,45 +1,46 @@
 import React from 'react'
-import PropTypes from 'prop-types'
+import {MdDelete, MdUndo} from 'react-icons/md'
+import stringifyPretty from 'json-stringify-pretty-compact'
 
 import Block from './Block'
 import InputButton from './InputButton'
-import {MdDelete, MdUndo} from 'react-icons/md'
-import FieldString from './FieldString'
-
 import labelFromFieldName from './_labelFromFieldName'
-import stringifyPretty from 'json-stringify-pretty-compact'
 import FieldJson from './FieldJson'
 
 
-export default class ExpressionProperty extends React.Component {
-  static propTypes = {
-    onDelete: PropTypes.func,
-    fieldName: PropTypes.string,
-    fieldType: PropTypes.string,
-    fieldSpec: PropTypes.object,
-    value: PropTypes.any,
-    errors: PropTypes.object,
-    onChange: PropTypes.func,
-    onUndo: PropTypes.func,
-    canUndo: PropTypes.func,
-    onFocus: PropTypes.func,
-    onBlur: PropTypes.func,
-  }
+type ExpressionPropertyProps = {
+  onDelete?(...args: unknown[]): unknown
+  fieldName: string
+  fieldType?: string
+  fieldSpec?: object
+  value?: any
+  errors?: {[key: string]: any}
+  onChange?(...args: unknown[]): unknown
+  onUndo?(...args: unknown[]): unknown
+  canUndo?(...args: unknown[]): unknown
+  onFocus?(...args: unknown[]): unknown
+  onBlur?(...args: unknown[]): unknown
+};
+
+type ExpressionPropertyState = {
+  jsonError: boolean
+};
 
+export default class ExpressionProperty extends React.Component<ExpressionPropertyProps, ExpressionPropertyState> {
   static defaultProps = {
     errors: {},
     onFocus: () => {},
     onBlur: () => {},
   }
 
-  constructor (props) {
-    super();
+  constructor (props:ExpressionPropertyProps) {
+    super(props);
     this.state = {
       jsonError: false,
     };
   }
 
-  onJSONInvalid = (err) => {
+  onJSONInvalid = (_err: Error) => {
     this.setState({
       jsonError: true,
     })
@@ -82,11 +83,11 @@ export default class ExpressionProperty extends React.Component {
 
     const fieldKey = fieldType === undefined ? fieldName : `${fieldType}.${fieldName}`;
 
-    const fieldError = errors[fieldKey];
+    const fieldError = errors![fieldKey];
     const errorKeyStart = `${fieldKey}[`;
     const foundErrors = [];
 
-    function getValue (data) {
+    function getValue(data: any) {
       return stringifyPretty(data, {indent: 2, maxLength: 38})
     }
     
@@ -94,11 +95,11 @@ export default class ExpressionProperty extends React.Component {
       foundErrors.push({message: "Invalid JSON"});
     }
     else {
-      Object.entries(errors)
-      .filter(([key, error]) => {
+      Object.entries(errors!)
+      .filter(([key, _error]) => {
         return key.startsWith(errorKeyStart);
       })
-      .forEach(([key, error]) => {
+      .forEach(([_key, error]) => {
         return foundErrors.push(error);
       })
 
diff --git a/src/components/_ZoomProperty.jsx b/src/components/_ZoomProperty.tsx
similarity index 71%
rename from src/components/_ZoomProperty.jsx
rename to src/components/_ZoomProperty.tsx
index 0101bb0da..54be2ab6d 100644
--- a/src/components/_ZoomProperty.jsx
+++ b/src/components/_ZoomProperty.tsx
@@ -1,5 +1,4 @@
 import React from 'react'
-import PropTypes from 'prop-types'
 import {mdiFunctionVariant, mdiTableRowPlusAfter} from '@mdi/js';
 import {latest} from '@maplibre/maplibre-gl-style-spec'
 
@@ -7,7 +6,6 @@ import InputButton from './InputButton'
 import InputSpec from './InputSpec'
 import InputNumber from './InputNumber'
 import InputSelect from './InputSelect'
-import FieldDocLabel from './FieldDocLabel'
 import Block from './Block'
 
 import DeleteStopButton from './_DeleteStopButton'
@@ -22,12 +20,12 @@ import sortNumerically from '../libs/sort-numerically'
  *
  * When the stops are reordered the references are also updated (see this.orderStops) this allows React to use the same key for the element and keep keyboard focus.
  */
-function setStopRefs(props, state) {
+function setStopRefs(props: ZoomPropertyProps, state: ZoomPropertyState) {
   // This is initialsed below only if required to improved performance.
-  let newRefs;
+  let newRefs: {[key: number]: string} = {};
 
-  if(props.value && props.value.stops) {
-    props.value.stops.forEach((val, idx) => {
+  if(props.value && (props.value as ZoomWithStops).stops) {
+    (props.value as ZoomWithStops).stops.forEach((_val, idx: number) => {
       if(!state.refs.hasOwnProperty(idx)) {
         if(!newRefs) {
           newRefs = {...state};
@@ -40,32 +38,39 @@ function setStopRefs(props, state) {
   return newRefs;
 }
 
+type ZoomWithStops = {
+  stops: [number | undefined, number][]
+  base?: number
+}
+
 
-export default class ZoomProperty extends React.Component {
-  static propTypes = {
-    onChange: PropTypes.func,
-    onDeleteStop: PropTypes.func,
-    onAddStop: PropTypes.func,
-    onExpressionClick: PropTypes.func,
-    fieldType: PropTypes.string,
-    fieldName: PropTypes.string,
-    fieldSpec: PropTypes.object,
-    errors: PropTypes.object,
-    value: PropTypes.oneOfType([
-      PropTypes.object,
-      PropTypes.string,
-      PropTypes.number,
-      PropTypes.bool,
-      PropTypes.array
-    ]),
+type ZoomPropertyProps = {
+  onChange?(...args: unknown[]): unknown
+  onChangeToDataFunction?(...args: unknown[]): unknown
+  onDeleteStop?(...args: unknown[]): unknown
+  onAddStop?(...args: unknown[]): unknown
+  onExpressionClick?(...args: unknown[]): unknown
+  fieldType?: string
+  fieldName: string
+  fieldSpec?: {
+    "property-type"?: string
+    "function-type"?: string
   }
+  errors?: object
+  value?: ZoomWithStops
+};
 
+type ZoomPropertyState = {
+  refs: {[key: number]: string}
+}
+
+export default class ZoomProperty extends React.Component<ZoomPropertyProps, ZoomPropertyState> {
   static defaultProps = {
     errors: {},
   }
 
   state = {
-    refs: {}
+    refs: {} as {[key: number]: string}
   }
 
   componentDidMount() {
@@ -78,7 +83,7 @@ export default class ZoomProperty extends React.Component {
     }
   }
 
-  static getDerivedStateFromProps(props, state) {
+  static getDerivedStateFromProps(props: ZoomPropertyProps, state: ZoomPropertyState) {
     const newRefs = setStopRefs(props, state);
     if(newRefs) {
       return {
@@ -89,7 +94,7 @@ export default class ZoomProperty extends React.Component {
   }
 
   // Order the stops altering the refs to reflect their new position.
-  orderStopsByZoom(stops) {
+  orderStopsByZoom(stops: ZoomWithStops["stops"]) {
     const mappedWithRef = stops
       .map((stop, idx) => {
         return {
@@ -98,10 +103,10 @@ export default class ZoomProperty extends React.Component {
         }
       })
     // Sort by zoom
-      .sort((a, b) => sortNumerically(a.data[0], b.data[0]));
+      .sort((a, b) => sortNumerically(a.data[0]!, b.data[0]!));
 
     // Fetch the new position of the stops
-    const newRefs = {};
+    const newRefs: {[key:number]: string} = {};
     mappedWithRef
       .forEach((stop, idx) =>{
         newRefs[idx] = stop.ref;
@@ -114,20 +119,20 @@ export default class ZoomProperty extends React.Component {
     return mappedWithRef.map((item) => item.data);
   }
 
-  changeZoomStop(changeIdx, stopData, value) {
-    const stops = this.props.value.stops.slice(0);
+  changeZoomStop(changeIdx: number, stopData: number | undefined, value: number) {
+    const stops = (this.props.value as ZoomWithStops).stops.slice(0);
     stops[changeIdx] = [stopData, value];
 
     const orderedStops = this.orderStopsByZoom(stops);
 
     const changedValue = {
-      ...this.props.value,
+      ...this.props.value as ZoomWithStops,
       stops: orderedStops
     }
-    this.props.onChange(this.props.fieldName, changedValue)
+    this.props.onChange!(this.props.fieldName, changedValue)
   }
 
-  changeBase(newValue) {
+  changeBase(newValue: number | undefined) {
     const changedValue = {
       ...this.props.value,
       base: newValue
@@ -136,33 +141,21 @@ export default class ZoomProperty extends React.Component {
     if (changedValue.base === undefined) {
       delete changedValue["base"];
     }
-    this.props.onChange(this.props.fieldName, changedValue)
+    this.props.onChange!(this.props.fieldName, changedValue)
   }
 
-  changeDataType = (type) => {
-    if (type !== "interpolate") {
+  changeDataType = (type: string) => {
+    if (type !== "interpolate" && this.props.onChangeToDataFunction) {
       this.props.onChangeToDataFunction(type);
     }
   }
 
   render() {
-    const {fieldName, fieldType, errors} = this.props;
-
-    const zoomFields = this.props.value.stops.map((stop, idx) => {
+    const zoomFields = this.props.value?.stops.map((stop, idx) => {
       const zoomLevel = stop[0]
       const key  = this.state.refs[idx];
       const value = stop[1]
-      const deleteStopBtn= <DeleteStopButton onClick={this.props.onDeleteStop.bind(this, idx)} />
-
-      const errorKeyStart = `${fieldType}.${fieldName}.stops[${idx}]`;
-      const foundErrors = Object.entries(errors).filter(([key, error]) => {
-        return key.startsWith(errorKeyStart);
-      });
-
-      const message = foundErrors.map(([key, error]) => {
-        return error.message;
-      }).join("");
-      const error = message ? {message} : undefined;
+      const deleteStopBtn= <DeleteStopButton onClick={this.props.onDeleteStop?.bind(this, idx)} />
 
       return <tr
         key={key}
@@ -180,9 +173,9 @@ export default class ZoomProperty extends React.Component {
           <InputSpec
             aria-label="Output value"
             fieldName={this.props.fieldName}
-            fieldSpec={this.props.fieldSpec}
+            fieldSpec={this.props.fieldSpec as any}
             value={value}
-            onChange={(_, newValue) => this.changeZoomStop(idx, zoomLevel, newValue)}
+            onChange={(_, newValue) => this.changeZoomStop(idx, zoomLevel, newValue as number)}
           />
         </td>
         <td>
@@ -204,7 +197,7 @@ export default class ZoomProperty extends React.Component {
                 value={"interpolate"}
                 onChange={propVal => this.changeDataType(propVal)}
                 title={"Select a type of data scale (default is 'categorical')."}
-                options={this.getDataFunctionTypes(this.props.fieldSpec)}
+                options={this.getDataFunctionTypes(this.props.fieldSpec!)}
               />
             </div>
           </Block>
@@ -215,8 +208,8 @@ export default class ZoomProperty extends React.Component {
               <InputSpec
                 fieldName={"base"}
                 fieldSpec={latest.function.base}
-                value={this.props.value.base}
-                onChange={(_, newValue) => this.changeBase(newValue)}
+                value={this.props.value?.base}
+                onChange={(_, newValue) => this.changeBase(newValue as number | undefined)}
               />
             </div>
           </Block>
@@ -226,7 +219,7 @@ export default class ZoomProperty extends React.Component {
               <thead>
                 <tr>
                   <th>Zoom</th>
-                  <th rowSpan="2">Output value</th>
+                  <th rowSpan={2}>Output value</th>
                 </tr>
               </thead>
               <tbody>
@@ -237,7 +230,7 @@ export default class ZoomProperty extends React.Component {
           <div className="maputnik-toolbox">
             <InputButton
               className="maputnik-add-stop"
-              onClick={this.props.onAddStop.bind(this)}
+              onClick={this.props.onAddStop?.bind(this)}
             >
               <svg style={{width:"14px", height:"14px", verticalAlign: "text-bottom"}} viewBox="0 0 24 24">
                 <path fill="currentColor" d={mdiTableRowPlusAfter} />
@@ -245,7 +238,7 @@ export default class ZoomProperty extends React.Component {
             </InputButton>
             <InputButton
               className="maputnik-add-stop"
-              onClick={this.props.onExpressionClick.bind(this)}
+              onClick={this.props.onExpressionClick?.bind(this)}
             >
               <svg style={{width:"14px", height:"14px", verticalAlign: "text-bottom"}} viewBox="0 0 24 24">
                 <path fill="currentColor" d={mdiFunctionVariant} />
@@ -257,7 +250,10 @@ export default class ZoomProperty extends React.Component {
     </div>
   }
 
-  getDataFunctionTypes(fieldSpec) {
+  getDataFunctionTypes(fieldSpec: {
+    "property-type"?: string
+    "function-type"?: string
+  }) {
     if (fieldSpec['property-type'] === 'data-driven') {
       return ["interpolate", "categorical", "interval", "exponential", "identity"];
     }
@@ -265,5 +261,4 @@ export default class ZoomProperty extends React.Component {
       return ["interpolate"];
     }
   }
-
 }
diff --git a/src/util/spec-helper.js b/src/util/spec-helper.ts
similarity index 72%
rename from src/util/spec-helper.js
rename to src/util/spec-helper.ts
index acf2779db..2574d28a2 100644
--- a/src/util/spec-helper.js
+++ b/src/util/spec-helper.ts
@@ -1,7 +1,7 @@
 /**
  * If we don't have a default value just make one up
  */
-export function findDefaultFromSpec (spec) {
+export function findDefaultFromSpec(spec: { type: 'string' | 'color' | 'boolean' | 'array', default?: any }) {
   if (spec.hasOwnProperty('default')) {
     return spec.default;
   }