Javascript: How to write a function that will be executed asynchronously?

问题

I have a few lines of code that I want to run asynchronously in Javascript so that it doesn't slow down my main algorithm. See this pseudo code:

//main algorithm with critical code that should run as soon as possible
...
...
runInParallel(function(){
  //time consuming unimportant code to shows some progress feedback to user
  ...
}
//the rest of the time critical algorithm
...
...
runInParallel(function(){
  //time consuming unimportant code to shows some progress feedback to user
  ...
}
//and so on and so forth

I searched Stackoverflow for how to write asynchronous code in Javascript but the following questions are not similar to mine:

• how to run a javascript function asynchronously, without using setTimeout?: it's about server side
• Loading javascript asynchronously - How to do callbacks?: it's about loading source code

I guess I can use timers for this purpose. All I want is the body of the function runInParallel() that runs a code efficiently in parallel with my main algorithm with lower priority if possible. Anyone?

回答1:

Javascript has no synchronization / thread management. If you wish to execute something asynchronously, you can use setTimeout combined with a callback to be notified when the function 's finished.

 var asyncHandle = setTimeout(function () { asyncCode(); callback(); }, 10);

The asyncHandle can be used to cancel the timeout prior to the function being called.

回答2:

If you're targeting HTML5 supporting browsers, go with HTML5 Web Workers.

You can also try this interesting, but quite old JavaScript compiler that allows a language extension for this purpose.

来源：https://stackoverflow.com/questions/9614953/javascript-how-to-write-a-function-that-will-be-executed-asynchronously