如何在javascript中向一个函数添加一个回调 [英] How to add a callback to a function in javascript

问题描述

我有两个javascript函数

  function one（）{
 do something long ... like writing jpgfile在磁盘上
} 
 
 function two（）{
 do something fast ... like show the file 
} 
  
 
 
 
我这样调用它（在jQuery中）
  one（）; 
 two（）; 
  
因为函数二需要函数一的链接文件，所以我需要确保执行完成。 ..所以获取函数两个在函数的回调函数一个应该是骗子..但是如何这样做？
 
 
 
注意：我做了一个警报'）之间的两个函数，让函数一个完成，它工作正常...当警报被注释（删除）没有什么工作了！
解决方案
你只需要使用一个回调，如果你正在做一些异步，否则不管多长时间，下一个函数将不会运行，直到第一个完成。
 
 
 
一个回调只是传递一个函数作为参数，然后在完成后调用它。
  function one（callback）{
 do something long ... like writing jpgfile on disk 
 callback（）; 
} 
 
 function two（）{
 do something fast ... like show the file 
} 
 
 one（two）; 
  
显然，如果你是做异步的，会告诉你什么时候完成（例如事件触发）。
 
I have two javascript functions
function one () {
   do something long... like writing jpgfile on disk
}

function two () {
   do something fast... like show the file
}
I call it (in jQuery) like this
 one ();
 two ();
Because function two needs the link file from function one, i need to be sure the execution is completed... so getting the function two in the callback of function one should be the trick.. but how to do that ?

note : I did put an alert ('aaa') between those two functions to let function one complete, and it worked fine... when the alert is commented (removed) nothing works anymore !
解决方案
You only need to use a callback if you are doing something asynchronous, otherwise it doesn't matter how long something takes, the next function won't run until the first has finished.

A callback is just passing a function as an argument, and then calling it when done.
function one (callback) {
   do something long... like writing jpgfile on disk
   callback();
}

function two () {
   do something fast... like show the file
}

one(two);
Obviously, if you are doing something asynchronous, then you need something that will tell you when it is finished (such as an event firing).

                        
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