常用的循环遍历

目录

• forEach()
• map()
• for of
• filter() || findIndex
• some() || every()
• reduce || reduceRight()

forEach()

遍历数组

arr.forEach((el,ix) => {})

map()

遍历并返回处理后的数组

arr.map((el,ix) => {})

for of

for(let item of res){
    console.log(item);
}

filter() || findIndex

返回符合条件所有元素的数组

arr.filter((el,ix) => {})

some() || every()

检测数组元素中是否有元素符合指定条件,返回逻辑值

• every:一假即假
• some:一真即真

const hasOneOf = (targetarr, arr) => {
    return targetarr.some(_ => arr.indexOf(_) > -1)
};

reduce || reduceRight()

函数作为累加器-从左到右

var result = [
    {subject: 'math',score: 88},
    {subject: 'chinese',score: 95},
    {subject: 'english',score: 80}
];
result.reduce(function(res, cus){
    res[cus.subject] = cus.score;
    return res;
},{});

var arrString = 'abcdaabc';
arrString.split('').reduce(function(res, cur) {
    res[cur] ? res[cur] ++ : res[cur] = 1
    return res;
}, {})