Question

I see there are lot’s of threads here in SO about asking for a javascript sleep function and I know it can be done only using setTimeout and setInterval.

I do some userscripting with greasemonkey and written a script that loads a lot of pages and calculates something from them. It works, but I don’t want to request the pages too fast.

var html0=syncGet(url0); // custom function for sync ajax call.
// fill the something array
for(var i=0;i<something.length;i++)
{
   // calculate url1,url2 using the array and the i variable
   // do something with lots of local variables
   var html1=syncGet(url1);
   // I would put a sleep here.
   // do something with the results
   var html2=syncGet(url2);
   // I would put a sleep here.
   // do something with the results
   // get url3 from the page loaded from url2
   var html3=syncGet(url3);
   // I would put a sleep here.
   // do something with the results
}
// use the result of the for loop and lots of code will follow...

The actual code is a bit more complex and longer than this.

I’m crying for the nonexistent sleep function (and understand why is it not possible) How to refactor this to use setTimeout, setInterval functions and keep it readable (and working) too?

Answer 1

I had a similar problem where a big loop was blocking the whole browser in some older browsers, I solved it using :

function handlenext(idx,length) {
    idx++

    //do your stuff here base on idx.


    if (idx < length) {
        setTimeout(function(){handlenext(idx,length)},1)
    } else {
        initSuccessEnd()
    }
}

var ln = something.length;


if (ln>0) {
    handlenext(0,ln);
} else {
    initSuccessEnd()
}

here initSuccessEnd is a callback function called when all is finished ..