### 循环性能对比

let index = 0;
let arr = [];
while (index < 100000) {
arr.push(index);
index++;
}

console.time('one');
for (let i = 0; i < arr.length; i++) {
    // arr[i]
}
console.timeEnd('one');
// one: 2.09765625ms

console.time('two');
for (let i = 0, len = arr.length; i < len; i++) {
    // arr[i]
}
console.timeEnd('two');
// two: 0.839111328125ms

console.time('three');
for (let i = 0, item; item = arr[i++];) {
    // console.log(arr[i])
}
console.timeEnd('three');
// three: 0.004150390625ms