JavaScript数组去重方法

摘要：一利用去重中最常用二利用嵌套，然后去重中最常用第一个等同于第二个，方法删除第二个和没有去重，两个直接消失了三利用去重没有去重四利用没有去重五利用对象的属性不能相同的特点进行去重两个直接去掉了，和去重六利用检测数组是否有某个值没有去重

一、利用ES6 Set去重（ES6中最常用）

function unique (arr) {
  return Array.from(new Set(arr))
}
var arr = [1,1,"true","true",true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,"NaN", 0, 0, "a", "a",{},{}];
console.log(unique(arr))
//[1, "true", true, 15, false, undefined, null, NaN, "NaN", 0, "a", {}, {}]

二、利用for嵌套for，然后splice去重（ES5中最常用）

function unique(arr){            
    for(var i=0; i
三、利用indexOf去重
function unique(arr) {
    if (!Array.isArray(arr)) {
        console.log("type error!")
        return
    }
    var array = [];
    for (var i = 0; i < arr.length; i++) {
        if (array .indexOf(arr[i]) === -1) {
            array .push(arr[i])
        }
    }
    return array;
}
var arr = [1,1,"true","true",true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,"NaN", 0, 0, "a", "a",{},{}];
console.log(unique(arr))
// [1, "true", true, 15, false, undefined, null, NaN, NaN, "NaN", 0, "a", {…}, {…}]  //NaN、{}没有去重 

四、利用sort()
function unique(arr) {
    if (!Array.isArray(arr)) {
        console.log("type error!")
        return;
    }
    arr = arr.sort()
    var arrry= [arr[0]];
    for (var i = 1; i < arr.length; i++) {
        if (arr[i] !== arr[i-1]) {
            arrry.push(arr[i]);
        }
    }
    return arrry;
}
var arr = [1,1,"true","true",true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,"NaN", 0, 0, "a", "a",{},{}];
console.log(unique(arr))
// [0, 1, 15, "NaN", NaN, NaN, {…}, {…}, "a", false, null, true, "true", undefined]      //NaN、{}没有去重

五、利用对象的属性不能相同的特点进行去重
function unique(arr) {
    if (!Array.isArray(arr)) {
        console.log("type error!")
        return
    }
    var arrry= [];
     var  obj = {};
    for (var i = 0; i < arr.length; i++) {
        if (!obj[arr[i]]) {
            arrry.push(arr[i])
            obj[arr[i]] = 1
        } else {
            obj[arr[i]]++
        }
    }
    return arrry;
}
var arr = [1,1,"true","true",true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,"NaN", 0, 0, "a", "a",{},{}];
console.log(unique(arr))
//[1, "true", 15, false, undefined, null, NaN, 0, "a", {…}]    //两个true直接去掉了，NaN和{}去重

六、利用includes
function unique(arr) {
    if (!Array.isArray(arr)) {
        console.log("type error!")
        return
    }
    var array =[];
    for(var i = 0; i < arr.length; i++) {
            if( !array.includes( arr[i]) ) {//includes 检测数组是否有某个值
                    array.push(arr[i]);
              }
    }
    return array
}
var arr = [1,1,"true","true",true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,"NaN", 0, 0, "a", "a",{},{}];
console.log(unique(arr))
//[1, "true", true, 15, false, undefined, null, NaN, "NaN", 0, "a", {…}, {…}]     //{}没有去重

七、利用hasOwnProperty
function unique(arr) {
    var obj = {};
    return arr.filter(function(item, index, arr){
        return obj.hasOwnProperty(typeof item + item) ? false : (obj[typeof item + item] = true)
    })
}
var arr = [1,1,"true","true",true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,"NaN", 0, 0, "a", "a",{},{}];
console.log(unique(arr))
//[1, "true", true, 15, false, undefined, null, NaN, "NaN", 0, "a", {…}]   //所有的都去重了

八、利用filter
function unique(arr) {
  return arr.filter(function(item, index, arr) {
    //当前元素，在原始数组中的第一个索引==当前索引值，否则返回当前元素
    return arr.indexOf(item, 0) === index;
  });
}
var arr = [1,1,"true","true",true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,"NaN", 0, 0, "a", "a",{},{}];
console.log(unique(arr))
//[1, "true", true, 15, false, undefined, null, "NaN", 0, "a", {…}, {…}]

九、利用递归去重
function unique(arr) {
        var array= arr;
        var len = array.length;

    array.sort(function(a,b){   //排序后更加方便去重
        return a - b;
    })

    function loop(index){
        if(index >= 1){
            if(array[index] === array[index-1]){
                array.splice(index,1);
            }
            loop(index - 1);    //递归loop，然后数组去重
        }
    }
    loop(len-1);
    return array;
}
var arr = [1,1,"true","true",true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,"NaN", 0, 0, "a", "a",{},{}];
console.log(unique(arr))
//[1, "a", "true", true, 15, false, 1, {…}, null, NaN, NaN, "NaN", 0, "a", {…}, undefined]

十、利用Map数据结构去重
function arrayNonRepeatfy(arr) {
  let map = new Map();
  let array = new Array();  // 数组用于返回结果
  for (let i = 0; i < arr.length; i++) {
    if(map .has(arr[i])) {  // 如果有该key值
      map .set(arr[i], true); 
    } else { 
      map .set(arr[i], false);   // 如果没有该key值
      array .push(arr[i]);
    }
  } 
  return array ;
}
var arr = [1,1,"true","true",true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,"NaN", 0, 0, "a", "a",{},{}];
console.log(unique(arr))
//[1, "a", "true", true, 15, false, 1, {…}, null, NaN, NaN, "NaN", 0, "a", {…}, undefined]

十一、利用reduce+includes
function unique(arr){
    return arr.reduce((prev,cur) => prev.includes(cur) ? prev : [...prev,cur],[]);
}
var arr = [1,1,"true","true",true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,"NaN", 0, 0, "a", "a",{},{}];
console.log(unique(arr));
// [1, "true", true, 15, false, undefined, null, NaN, "NaN", 0, "a", {…}, {…}]

十二、[…new Set(arr)]
[...new Set(arr)] 
//代码就是这么少----（其实，严格来说并不算是一种，相对于第一种方法来说只是简化了代码）