JavaScript常用数组去重的方法及对比详解_javascript技巧_

 const arr = [ 1, 1, "1", "1", 0, 0, "0", "0", true, false, "true", "false", "a", "A", undefined, undefined, "undefined", null, null, 'null', NaN, NaN, +0, -0, new String("1"), new String("1"), Symbol(1), Symbol(1), {}, {}, /a/, /a/, [], [] ]; 

console.log(1 == "1"); // true console.log(1 === "1"); // false console.log(0 == "0"); // true console.log(0 === "0"); // false console.log(0 == +0); // true console.log(0 === +0); // true console.log(0 == -0); // true console.log(0 === -0); // true console.log(+0 == -0); // true console.log(+0 === -0); // true console.log(0 == false); // true console.log(0 === false); // false console.log(0 == undefined); // false console.log(0 === undefined); // false console.log(0 == null); // false console.log(0 === null); // false console.log(1 == true); // true console.log(1 === true); // false console.log(undefined == null); // true console.log(undefined === null); // false console.log(NaN == NaN); // false console.log(NaN === NaN); // false console.log(new String("1") == new String("1")); // false console.log(new String("1") === new String("1")); // false Object.prototype.toString.call(new String('1')) // '[object String]' console.log(/a/ == /a/); // false console.log(/a/ === /a/); // false Object.prototype.toString.call(/a/); //'[object RegExp]' console.log(Symbol(1) == Symbol(1)); // false console.log(Symbol(1) === Symbol(1)); // false console.log({} == {}); // false console.log({} === {}); // false console.log([] == []); // false console.log([] === []); // false 

// 暴力解法一 function unique(array) { if (!Array.isArray(array)) { console.log("type error!"); return; } const res = [array[0]]; let arrLen = array.length; let resLen = res.length; for (let i = 0; i < arrLen; i++) { let flag = true; for (let j = 0; j < resLen; j++) { if (array[i] === res[j]) { flag = false; break; } } if (flag) { res.push(array[i]); resLen = res.length; } } return res; } // [1, '1', 0, '0', true, false, 'true', 'false', 'a', 'A', undefined, 'undefined', null, 'null', NaN, NaN, String {'1'}, String {'1'}, Symbol(1), Symbol(1), {}, {}, /a/, /a/, [], []] 

// ES6 Array.from + Set 方法一 function unique(array) { if (!Array.isArray(array)) { console.log('type error!') return } return Array.from(new Set(array)) } // ES6 点运算 + Set 方法二 function unique1(array) { if (!Array.isArray(array)) { console.log('type error!') return } return [...new Set(arr)] } // ES6 箭头函数 + 点运算 + Set 方法三 const unique2 = (array) => { if (!Array.isArray(array)) { console.log('type error!') return } return [...new Set(arr)] } // ES6 Map + ES5 filter 方法四 function unique3(array) { if (!Array.isArray(array)) { console.log('type error!') return } const seen = new Map() return array.filter((a) => !seen.has(a) && seen.set(a, 1)) } 

// indexOf + forEach 利用indexOf检测元素在新数组是否存在 function unique(array) { if (!Array.isArray(array)) { console.log('type error!') return } const newArr = []; array.forEach((el) => { if (newArr.indexOf(el) === -1) { newArr.push(el); } }); return newArr; } 

// indexOf + forEach 利用indexOf检测元素在新数组是否存在 function unique(array) { if (!Array.isArray(array)) { console.log('type error!') return } return array.filter((item, index) => { return array.indexOf(item) === index; }); } console.log([NaN].indexOf(NaN)); // -1 

console.log([NaN].indexOf(NaN)); // -1 

// sort()方法不支持Symbol，Symbol不支持转换成字符串 function unique(array) { if (!Array.isArray(array)) { console.log("type error!"); return; } const sortArr = array.sort(); const newArr = []; sortArr.forEach((el, i) => { if (sortArr[i] !== sortArr[i - 1]) { newArr.push(el); } }); return newArr; } 

// 利用includes()方法检查新数组是否包含原数组的每一项 function unique(array) { if (!Array.isArray(array)) { console.log("type error!"); return; } const newArr = []; array.forEach((el) => { newArr.includes(el) ? newArr : newArr.push(el); }); return newArr; } 

// 利用includes()方法检查新数组是否包含原数组的每一项 function unique(array) { if (!Array.isArray(array)) { console.log("type error!"); return; } return array.reduce((pre, cur) => { !pre.includes(cur) && pre.push(cur); return pre; }, []); }