map和set写法

advanceJs/map.js

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+// 语法: new Map()
+
+let myMap = new Map();
+
+let keyObj = {};
+let keyFunc = function () {};
+let keyString = 'a string';
+
+myMap.set(keyString, '和键\'a string\'关联的值');
+myMap.set(keyObj, '和键keyObj关联的值');
+myMap.set(keyFunc, '和键keyFunc关联的值');
+
+console.log(myMap.get(keyString));
+console.log(myMap.get({})); //undefined
+console.log(myMap.get(() => {})); //undefined
+
+//NAN作为map键
+let myMap2 = new Map();
+myMap2.set(NaN, 'not a number');
+// console.log(myMap2.get(NaN)); // "not a number"
+
+let otherNaN = Number("foo");
+// console.log(otherNaN);
+// console.log(myMap2.get(otherNaN));  // "not a number"
+
+//for of 迭代Map
+for(let [key,value] of myMap){
+  console.log(key,value);
+}
+
+/**
+ * Map与数组互转 new Map() <=> [...map] Array.from(map)
+ */
+let kvArray = [["key1", "value1"], ["key2", "value2"]];
+let myApp3 = new Map(kvArray);
+console.log(myApp3.get("key1"));
+let array1 = Array.from(myApp3);
+let array2 = [...myApp3];
+console.log(array1,array2);
+console.log(Array.isArray(array1),Array.isArray(array2));
+
+/**
+ * 数组合并
+ */
+let first = new Map([[1, 'one'], [2, 'two'], [3, 'three'],]);
+
+let second = new Map([[1, 'uno'], [2, 'dos']]);
+
+// 合并两个Map对象时，如果有重复的键值，则后面的会覆盖前面的。
+// 展开运算符本质上是将Map对象转换成数组。
+let merged = new Map([...first, ...second]);
+
+console.log(merged.get(1)); // uno
+console.log(merged.get(2)); // dos
+console.log(merged.get(3)); // three
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advanceJs/set.js

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+/*
+ * 语法:new Set([iterable]);
+ */
+
+let mySet = new Set();
+
+mySet.add(1);
+mySet.add(5);
+mySet.add(5);
+mySet.add('some text');
+let o = {
+  a: 1,
+  b: 2,
+};
+mySet.add(o);
+mySet.add(o);
+
+// console.log(mySet);
+
+mySet.has(1); //true
+mySet.has(o); //true
+
+// mySet.delete(o); //true，删除o
+// mySet.size; //3
+
+/**
+ * Set与Array互转
+ */
+let mySet2 = new Set([1, 2, 3, 4, {
+  a: 1,
+  b: 2,
+}]);
+let arr = [...mySet2];
+
+/**
+ * set1与set2求交集
+ */
+let x = new Set([...mySet].filter(v => mySet2.has(v)));
+console.log(x);
+
+/**
+ * set1与set2求并集
+ */
+let difference = new Set([...mySet].filter(v => !mySet2.has(v)));
+
+let x1 = new Set([{id:1},{id:2}])
+let x2 = new Set([{id:1},{id:3}])
+let x3 = new Set([...x1].filter(v => !x2.has(v)));
+console.log(x3);
+
+let a1 = [{id:1},{id:2}]
+let a2 = [{id:1},{id:3}]
+for(const item1 of a2){  //循环json数组对象的内容
+
+  let flag = true;  //建立标记，判断数据是否重复，true为不重复
+
+  for(const item2 of a1){  //循环新数组的内容
+
+    if(item1.id==item2.id){ //让json数组对象的内容与新数组的内容作比较，相同的话，改变标记为false
+      flag = false;
+    }
+
+  }
+
+  if(flag){ //判断是否重复
+    a1.push(item1); //不重复的放入新数组。  新数组的内容会继续进行上边的循环。
+  }
+
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+}
+console.log(a1);
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