数组去重

数组去重

使用filter

我们根据数组api filter()与indexOf()来去重

function fn1(a,b){
    let arr1 = a.concat(b);
    let info = arr1.filter((item,index)=>{
        return arr1.indexOf(item) === index;
    })
    return info;
}

使用forEach()或者for循环+indexOf()

//使用forEach()api
function fn1(a,b){
    let arr1 = a.concat(b);
    let arr = [];
    arr1.forEach(item => {
        if(arr.indexOf(item) == -1){
            arr.push(item);
        }
    });
    return arr;
}

//使用for循环
function fn2(a,b){
    let arr1 = a.concat(b);
    let arr = [];
    for(let i = 0 ; i < arr1.length ; i++){
        if(arr.indexOf(arr1[i]) == -1){
            arr.push(arr1[i]);
        }
    }
    return arr;
}

for循环嵌套

function fn1(a,b){
    let arr1 = a.concat(b);
    for(let i = 0 ; i < arr1.length ; i++){
        for(let j = i+1 ; j < arr1.length ; j++){
            if(arr1[i] == arr1[j]){
                arr1.splice(j,1);
                j--;
            }
        }
    }
    return arr1;
}

使用sort()

function fn1(a,b){
    let arr1 = a.concat(b);
    arr1.sort();
    let arr = [];
    for(let i = 1 ; i < arr1.length ; i++){
        if(arr1[i-1] !== arr1[i]){
            arr.push(arr1[i]);
        }
    }
    return arr;
}

es6 Set方法

function fn1(a,b){
    let arr1 = a.concat(b);
    let info = [...new Set(arr1)];
    return info;
}

for...of 与object

利用了object对象的key值的唯一性

function fn1(a,b){
    let arr1 = a.concat(b);
    let res = [];
    let obj = {};
    for(let i of arr1){
        let k = typeof(i) + i;
        if(!obj[k]){
            res.push(i);
            obj[k] = 1;
        }
    }
    return res;
}