JavaScript之数组去重

[heyushuo]

1.利用对象的属性不能相同的特点进行去重(兼容性好)

var arr = [1, 6, 4, 6, 6, 4, 2, "a", "a"];
var array = [];
var obj = {};
for (var i = 0; i < arr.length; i++) {
  if (!obj[arr[i]]) {
    obj[arr[i]] = true;
    array.push(arr[i]);
  }
}
console.log(array); //[1, 6, 4, 2, "a"]

2.双层循环 (兼容性好)

var arr = [1, 6, 4, 6, 6, 4, 2, "a", "a"];
var array = [];
for (var i = 0; i < arr.length; i++) {
  for (var j = 0; j < array.length; j++) {
    if (arr[i] == array[j]) {
      break;
    }
  }
  //如果这两个数相等说明循环完了,没有相等的元素
  if (j == array.length) {
    array.push(arr[i]);
  }
}
console.log(array); //[1, 6, 4, 2, "a"]

3.利用 indexOf()

var arr = [1, 6, 4, 6, 6, 4, 2, "a", "a"];
var array = [];
for (var i = 0; i < arr.length; i++) {
  if (array.indexOf(arr[i]) == -1) {
    array.push(arr[i]);
  }
}
console.log(array); //[1, 6, 4, 2, "a"]

4.利用 forEach 和 indexOf()

var arr = [1, 6, 4, 6, 6, 4, 2, "a", "a"];
var array = [];
arr.forEach(function(item, index) {
  if (array.indexOf(item) == -1) {
    array.push(item);
  }
});
console.log(array); //[1, 6, 4, 2, "a"]

5.利用 filter()和 indexOf()

var arr = [1, 6, 4, 6, 6, 4, 2, "a", "a"];
var array = arr.filter(function(item, index) {
  return arr.indexOf(item) == index;
});
console.log(array); //[1, 6, 4, 2, "a"]

6.ES6 的 new Set()实现去重

var arr = [1, 6, 4, 6, 6, 4, 2, "a", "a"];
//第一种
var newarr = Array.from(new Set(arr));
console.log(newarr); //[1, 6, 4, 2, "a"]
//第二种
var newarr1 = [...new Set(arr)];
console.log(newarr1); //[1, 6, 4, 2, "a"]

7.ES6 的 includes 实现去重

var arr = [1, 6, 4, 6, 6, 4, 2, "a", "a"];
var array = [];
arr.forEach(function(item, index) {
  if (!array.includes(item)) {
    array.push(item);
  }
});
console.log(array); //[1, 6, 4, 2, "a"]