# 小技巧：for of中获取index
日常开发中在遍历数据时经常使用for...of,forEach
前者使用时能够配合async await,continue,break等等
const data = [
{ name: 'xm1', age: 1 },
{ name: 'xm2', age: 4 },
{ name: 'xm3', age: 5 },
{ name: 'xm4', age: 9 }
]
function sleep(s){
const end = s * 1000 + Date.now()
while(Date.now() < end){}
}
async function fn(){
for (const people of data) {
if (people.age === 9) {
break
}
if (people.age % 2 !== 0) {
continue
}
await sleep(people.age)
console.log(people.name);
}
}
fn() // xm2
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但有时候想获取元素的idx，有哪些简单的方式呢
# 1-Array.prototype.map
function MapWithIdx(arr){
return arr.map((v, idx) => ([idx, v]))
}
for (const [idx, v] of MapWithIdx(data)) {
console.log(idx, v);
}
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# 2-Array.prototype.entries
这个方法是ES6新增的API
for (const [idx, v] of data.entries()) {
console.log(idx, v);
}
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# 3-Array.prototype.keys
这个方法也是ES6新增的API
for (const idx of data.keys()) {
const v = data[idx]
console.log(idx, v);
}
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