Javascript Execution Timing

函数的执行时机

1. 解释为什么如下代码会打印 6 个 6

   let i = 0
   for(i = 0; i<6; i++){
     setTimeout(()=>{
    console.log(i)
     },0)
   }
   

答： setTimeout会等到for loop的 i < 6 一直循环完，才会执行，setTimeout在这里就像个闹钟，只有等到 for loop循环完，setTimeout这个闹钟才会执行。

setTimeout function in Javascript usually takes a callback function as an argument. A callback function is a function that is executed after another function finishes running. In this case, it will run after for loop finishes. At this point, i is already 5 when the console.log([array[i]) is about to be executed. Due to the Closure of javascript, the console.log has access to the i = 5 which is defined as an other outer layer of the setTimeout.

1. 写出让上面代码打印 0、1、2、3、4、5 的方法

   for(let i = 0; i<6; i++){
     setTimeout(()=>{
    console.log(i)
     },0)
   }