js---Array对象的常用遍历方法

1.forEach(),遍历数组的每个元素

    let arrFor = ['muzi','digbig','muzidigbig','lucky']
    //forEach(),遍历数组的每个元素
    arrFor.forEach((item,index) => {
        console.log(`${index}---${item}`)
    })

2.map(参数为回调函数)函数，遍历数组每个元素，并回调操作，需要返回值，返回值组成新数组，原数组不变；

    let arr = [{id:1,name:'muzi'},{id:2,name:'digbig'},{id:3,name:'muzidigbig'},{id:4,name:'lucky'}]
    const arrMap = arr.map((item,index) => {
        return {
            id:item.id,
            name:item.name,
            sex:'男'
        }
    })
    console.log(arrMap)

3.filter(参数为回调函数)函数：过滤通过条件的元素组成一个新数组，原数组不变；

    let arr = [{id:1,name:'muzi'},{id:2,name:'digbig'},{id:3,name:'muzidigbig'},{id:4,name:'lucky'}]
    const arrFilter = arr.filter((item,index) => {
        return item.id >= 2;
    })
    console.log(arrFilter)

4.some(参数为回调函数)函数，遍历数组中是否有符合条件的函数，返回布尔值；

    let arr = [{id:1,name:'muzi'},{id:2,name:'digbig'},{id:3,name:'muzidigbig'},{id:4,name:'lucky'}]
    const arrSome = arr.some((item,index) => {
        return item.id === 5
    })
    console.log(arrSome)

5.every(参数为回调函数)函数，遍历数组是否每个元素都符合条件，返回布尔值；

    let arr = [{id:1,name:'muzi'},{id:2,name:'digbig'},{id:3,name:'muzidigbig'},{id:4,name:'lucky'}]
    const arrEvery = arr.every((item,index) => {
        return item.id >= 1
    })
    console.log(arrEvery)

6.find()函数，数组中的每个元素都执行这个回调函数；返回第一个满足条件的元素之后的元素就不在调用；没有符合的返回undefined；并没有改变数组的原始值。

    let arr = [{id:1,name:'muzi'},{id:2,name:'digbig'},{id:3,name:'muzidigbig'},{id:4,name:'lucky'}]
    const arrFind = arr.find((item,index) => {
        return item.id === 1
    })
    console.log(arrFind)

7.reduce(),合并二维数组

    var twoArr = [['mu','zi'],['dig','big'],['lucky','jiji']];
    var oneArr = twoArr.reduce(function(total,currentValue){
        // console.log(total)
        return total.concat(currentValue);
    },[])
    console.log(oneArr);//["mu", "zi", "dig", "big", "lucky", "jiji"]

js---Array对象的常用遍历方法

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