數組去重
面試中經常問的一道題，使用JS寫一個函數，對數組進行去重。
1.使用ES6的new Set()方式
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> </head> <body> <script> let arr = [1,1,2,2,3,3,4,4,5,5]; function unique(arr){ return new Set(arr) } let res = unique(arr); console.log(res); </script> </body> </html>
2.使用數組的indexOf方法進行去重
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> </head> <body> <script> let arr = [1,1,1,2,3,3,4,11,112,332,332,2,2,3,3,4,4,5,5]; /* 思路： 1.創建一個空的數組 2.對arr的數據進行循環遍歷，判斷空數組是否有arr的值，沒有就push進去 */ let uniqueArr = []; arr.map(item=>{ // console.log(item); uniqueArr.indexOf(item) == -1 ? uniqueArr.push(item) : ""; }) console.log(uniqueArr); </script> </body> </html>
數組對象去重
1.使用reduce對數組對象去重
let log = console.log.bind(console); let person = [ {id: 0, name: "小明"}, {id: 1, name: "小張"}, {id: 2, name: "小李"}, {id: 3, name: "小孫"}, {id: 1, name: "小周"}, {id: 2, name: "小陳"}, ]; let obj = {}; person = person.reduce((cur,next) => { obj[next.id] ? "" : obj[next.id] = true && cur.push(next); return cur; },[]) //設置cur默認類型為數組，並且初始值為空的數組 log(person);
2.使用reduce對數組字符串去重且保留2個相同的屬性值
去重前：
去重后：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> </head> <body> <script> let person = [{ 'age': 41, 'id': 12, }, { 'age': 20, 'id': 12, }, { 'age': 23, 'id': 12, }, { 'age': 25, 'id': 15, }, { 'age': 30, 'id': 15, }, { 'age': 12, 'id': 20, }, ]; let log = console.log.bind(console.log); let obj = {}; let obj2 = {}; let peon2 = []; let peon = person.reduce((cur, next) => { // 這里三元表達式的""表示什么也不操作 這里的next'id'就意味着這個程序就是根據next.'id'進行去重； // obj[next.id] ? "" : obj[next.id] = true && cur.push(next); if (obj[next.id]) { // 判斷數組對象里面的ID是否存在，如果存在，就追加到peon2數組中 peon2.push(next); } else { obj[next.id] = true && cur.push(next); } // log(obj); return cur; }, []) // 設置cur默認類型為數組，並且返回值為空的數據 // 對數據再次進行去重 peon2 = peon2.reduce((cur, next) => { if (obj2[next.id]) { peon2.push(next); } else { obj2[next.id] = true && cur.push(next); } return cur; }, []) peon2.map(item => { peon.push(item); }) log(peon); </script> </body> </html>
更多資料：
- https://www.cnblogs.com/caideyipi/p/7679681.html
- https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce