/*1、利用ES6 Set去重（ES6中最常用）*/
function unique1(arr) {
return Array.from(new Set(arr)) //[1, "true", true, false, undefined, null, NaN, "NaN", 0, "a", {}, {}]
}
/*2.利用for嵌套for，然后splice去重（ES5中最常用）*/
function unique2(arr) {
for(var i = 0; i < arr.length; i++) {
for(var j = i + 1; j < arr.length; j++) {
if(arr[i] == arr[j]) {
arr.splice(j,1);
j--;
}
}
}
return arr; //[1, "true", false, undefined, NaN, NaN, "NaN", "a", {…}, {…}] //NaN和{}没有去重，两个null直接消失了
}
/*3.利用indexOf去重*/
function unique3(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; // [1, "true", true, false, undefined, null, NaN, NaN, "NaN", 0, "a", {…}, {…}] //NaN、{}没有去重
}
/*4 利用sort()*/
function unique4(arr) {
if(!Array.isArray(arr)) {
console.log('type error!')
return
}
arr = arr.sort()
var array = [arr[0]];
for(var i = 1; i < arr.length; i++) {
if(arr[i] !== arr[i-1]) {
array.push(arr[i]);
}
}
return array; // [0, 1, "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 unique5(arr) {
if(!Array.isArray(arr)) {
console.log('type error!')
return
}
var array = [];
var obj = {};
for(var i = 0; i < arr.length; i++) {
if(!obj[arr[i]]) {
array.push(arr[i])
obj[arr[i]] = 1;
}else {
obj[arr[i]] ++
}
}
return array; //[1, "true", false, undefined, null, NaN, 0, "a", {…}] //两个true直接去掉了，NaN和{}去重
}
/*六、利用includes*/
function unique6(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])) {
array.push(arr[i])
}
}
return array //[1, "true", true, false, undefined, null, NaN, "NaN", 0, "a", {…}, {…}] //{}没有去重
}
/*七、利用hasOwnProperty !!!所有的去重了*/
function unique7(arr) {
var obj = {};
return arr.filter(function(item,index,arr) {
return obj.hasOwnProperty(typeof item + item) ? false : (obj[typeof item + item] = true); //[1, "true", true, false, undefined, null, NaN, "NaN", 0, "a", {…}] 所有的都去重了
})
}
/*八、利用filter*/
function unique8(arr) {
return arr.filter(function(item, index, arr) {
return arr.indexOf(item, 0) === index; //[1, "true", true, false, undefined, null, "NaN", 0, "a", {…}, {…}]
});
}
/*九、利用递归去重*/
function unique9(arr) {
var array = arr;
var len = array.length;
array.sort(function(a,b) {
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; //[1, "a", "true", true, false, 1, {…}, null, NaN, NaN, "NaN", 0, "a", {…}, undefined]
}
/*十、利用Map数据结构去重*/
function unique10(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])) {
map.set(arr[i],true);
}else {
map.set(arr[i],false); //如果没有该key值；
array.push(arr[i]);
}
}
return array; //(12) [1, "true", true, false, undefined, null, NaN, "NaN", 0, "a", {…}, {…}]
}
/*十一、利用reduce+includes*/
function unique11(arr) {
return arr.reduce((prev,cur) => prev.includes(cur) ? prev : [...prev,cur],[]); //(12) [1, "true", true, false, undefined, null, NaN, "NaN", 0, "a", {…}, {…}]
}
/*十二、[...new Set(arr)]*/
function unique12(arr) {
return [...new Set(arr)] //(12) [1, "true", true, false, undefined, null, NaN, "NaN", 0, "a", {…}, {…}]
}
/*十三. lodash _.uniq([2, 1, 2]);// => [2, 1] 需要引入lodash*/