Why does setTimeout works for endless recursive calls?

Question

This is my recursive function :

function importTEI(index,data,header){
    if (index == data.length){return}

    var tei = new dhis2API.trackedEntityInstance();
    tei.excelImportPopulator(header,data[index]);
    tei.POST(requestCallback,requestCallback,index);

    function requestCallback(response){
        notificationCallback(response);
        setTimeout(function(){
            importTEI(response.importStat.index+1,importData,header);
        },0);
    }
}

The function importTEI is called within the function using setTimeout. When called without the setTimeout then after a few requests this error comes -

Uncaught RangeError: Maximum call stack size exceeded

But with setTimeout it runs forever....How come? What special thing is happening inside setTimeout? Is it no longer a recursive call?

Any tips are appreciated. Thnx.

Answer 1

It's no longer a recursive call. The setTimeout is a callback in the future and that call would be at the "top of the stack". The existing call to your function sets up this callback and then finishes its execution, resulting in zero recursion.