javascript数组的15种循环(包含ES5、ES6)

let list = [‘a‘, ‘b‘, ‘c‘, ‘d‘,‘e‘];
for (var i = 0; i < list.length; i++) {
     console.log(list[i])
 }
// a、b、c、d、e

let list = [‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘];
for (var i = list.length - 1; i > 0; i--) {
    if (i === 0) {
        continue;
    }
    if (i === 2) {
        break;
    }
    console.log(list[i])
}
// e、d

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘];
let i = 0;
while (i < list.length){
    console.log(list[i]);
    i++
} //‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘];
let i = 0;
do {
    console.log(list[i])
    i++;
} while (i < list.length) //‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘

let list = [‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘];
list.forEach((item,index,ary) => {
    console.log(`item:${item}----index:${index}----ary:${ary}`)
})

　　item:a----index:0----ary:a,b,c,d,e
　　item:b----index:1----ary:a,b,c,d,e
　　item:c----index:2----ary:a,b,c,d,e
　　item:d----index:3----ary:a,b,c,d,e
　　item:e----index:4----ary:a,b,c,d,e

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘];
const isPass = list.every((item,index) => {
    return typeof item === ‘string‘
})
console.log(isPass) // false 

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘];
const isPass = list.some((item,index) => {
    return typeof item === ‘boolean‘
})
console.log(isPass) //false

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘,‘a‘];
const result = list.indexOf(‘a2‘,2)
console.log(result) // 5

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘,‘a‘];
const result = list.lastIndexOf(‘a‘,2)
console.log(result) //0

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘];
const result = list.filter((item, index) => {
    return typeof item === ‘string‘
})
console.log(result) // ["a", "c", "d", "e", "a"]

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘];
const result = list.map((item, index) => {
    return item + ‘_‘
})
console.log(result) // ["a_", "12_", "c_", "d_", "e_", "a_"]

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘];
const result = list.reduce((total,prev,index,arr) => {
    return total + prev;
},‘‘);
console.log(‘result‘,result); //a12cdea

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘];
for(let key in list){
    console.log(list[key]);
} //‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘];

const result = list.find((item,index) => {
    return item === ‘a‘
})
console.log(result) // a

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘,‘a‘];
const result = list.findIndex((item,index) => {
    return item === ‘a‘
})
console.log(result)  // 0 

let list = [‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘];
for (let s of list) {
    console.log(s);
} //‘a‘, 12, ‘c‘, ‘d‘, ‘e‘, ‘a‘