去重（性能由高到低）
一、New Set()
let arr = [1,1,'true','true',true,true,15,15,false,false, undefined,undefined, null,null, NaN, NaN,'NaN', 0, 0, 'a', 'a',{},{}];
function unique(arr) {
return Array.from(new Set(arr));
}
console.log(unique(arr));// [1, "true", true, 15, false, undefined, null, NaN, "NaN", 0, "a", {…}, {…}]
二、Array.sort()
function unique(arr) {
arr = arr.sort();
let array = [arr[0]];
for (let i = 1; i < arr.length; i++) {
if (arr[i] !== arr[i-1]) {
array.push(arr[i]);
}
}
return array;
}
console.log(unique(arr));//[0, 1, 15, NaN, NaN, "NaN", {…}, {…}, "a", false, null, "true", true, undefined]
三、Array.indexOf()
function unique(arr) {
let array = [];
for (let i = 0; i < arr.length; i++) {
if (array.indexOf(arr[i]) === -1) {
array.push(arr[i]);
}
}
return array;
}
console.log(unique(arr));//[1, "true", true, 15, false, undefined, null, NaN, NaN, "NaN", 0, "a", {…}, {…}]
四、双重for循环
function unique(arr) {
for (let i = 0; i < arr.length; i++) {
for (let j = i+1; j < arr.length; j++) {
if (arr[i] === arr[j]) {
arr.splice(j, 1);
j--;
}
}
}
return arr;
}
console.log(unique(arr)); //[1, "true", true, 15, false, undefined, null, NaN, NaN, "NaN", 0, "a", {…}, {…}]
