数组方法

迭代器函数

every

会返回第一个false后中断执行

function isEven(x) {
    console.log(x);
    return (x % 2 == 0) ? true : false;
}

let num = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];

num.every(isEven);

some

会返回第一个true后中断执行

function isEven(x) {
    console.log(x);
    return (x % 2 == 0) ? true : false;
}

let num = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];

num.some(isEven);

forEach

与for的结果相同

let num = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];

num.forEach(function(item,index){

    console.log(x % 2 == 0);
    
});

map

myMap的值为[false,true,false,true,false,true,false,true,false,true,false,true,false,true,false],它保存了传入map方法的isEven函数的运行结果。

function isEven(x) {
    console.log(x);
    return (x % 2 == 0) ? true : false;
}

let num = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];

let myMap = num.map(isEven);

filter

myFilter返回的值为 [2,4,6,8,10,12,14]

function isEven(x) {
    console.log(x);
    return (x % 2 == 0) ? true : false;
}

let num = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];

let myFilter = num.filter(isEven);

reduce

targ 的值为200 ，可以获取前一个和后一个值

let num = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];

let targ = num.reduce(function (previsor, current, index) {
    return previsor + current;
});

搜索和排序

reverse

res为 [
15,
14,
13,
12,
11,
10,
9,
8,
7,
6,
5,
4,
3,
2,
1
]，数组内的元素发生反序

let num = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];
let res = num.reverse();

sort

排序

let num = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];
function compare(a,b) {
    return a-b;
}
num.sort(compare);

• 自定义排序

let info = [
    {name:'yinxs',age:25},
    {name:'yu',age:28},
    {name:'pan',age:27}
];
function compare(a,b) {
    return a.age - b.age;
}
info.sort(compare);

• 字符串排序

let info = ['Ana','John','ana'];
function compare(a,b) {
    if(a.toLowerCase() < b.toLowerCase()){
        return -1;
    }else if(a.toLowerCase() > b.toLowerCase()){
        return 1;
    }else{
        return 0;
    }
}
info.sort(compare);

搜索(lastIndexOf,indexOf)

indexOf返回第一个匹配的索引，lastIndexOf返回最后一个匹配的索引