Js数组去重的方法

1、ES6 Set方法去重

/**
 *  1、利用ES6 Set去重
 */
let arr = [1,2,3,25,4,1,2,3]
function deduplicationBySet(array) {
   // return Array.from(new Set(array))
    return [...new Set(arr)]
}
console.log(deduplicationBySet(arr)) // [1, 2, 3, 25, 4]

2、双重for循环去重

/**
 * 2、双重for循环去重
 */
let arr = [1,2,3,25,4,1,2,3]
function deduplicationByFor(array) {
    let len = array.length
    for (let i = 0; i<len; i++){
        for (let j = i+1;j<len; j++){
            if (arr[i] === arr[j]) {
                arr.splice(j,1)
                j-- // 每删除一个 要遍历的内容-1
                len-- // 每删除一个 数组长度-1
            }
        }
    }
    return array
}
console.log(deduplicationByFor(arr)) // [1, 2, 3, 25, 4]

3、indexOf实现去重

/**
 * 3、indexOf实现去重
 */
let arr = [1,2,3,25,4,1,2,3]
function deduplicationByIndexOf(array) {
    let arr = []
    for (let i = 0; i<array.length; i++) {
        if (arr.indexOf(array[i]) === -1){
            arr.push(array[i])
        }
    }
    return arr
}
console.log(deduplicationByIndexOf(arr)) // [1, 2, 3, 25, 4]

4、includes实现去重

/**
 * 4、includes实现去重
 */
let arr = [1,2,3,25,4,1,2,3]
function deduplicationByIncludes(array) {
    let arr = []
    for (let i = 0; i<array.length; i++) {
        if (!arr.includes(array[i])){
            arr.push(array[i])
        }
    }
    return arr
}

console.log(deduplicationByIncludes(arr)) // [1, 2, 3, 25, 4]

5、Filter实现去重

/**
 * 5、Filter实现去重
 */
let arr = [1,2,3,25,4,1,2,3]
function deduplicationByFilter(array) {
    return array.filter((item,index) => {
        // 将 元素在数组中第一次出现的索引值等于当前索引 的元素返回
         return array.indexOf(item,0) === index
     })
}
console.log(deduplicationByFilter(arr)) // [1, 2, 3, 25, 4]