javascript：重试直到承诺解决为止，然后执行

Question

I am checking whether some elements of my DOM are fully charged and I wanted to do it through a promise function that checks some elements and if not loaded waits for them.

This is my code

var jq = jQuery.noConflict();
var df = jq.Deferred();
function keepTrying() {
try{
var el1 = \\element to search for
var success=true
catch(e){
var success= false
}
if (success) {
    //Resolves promises
    df.resolve();
    return df.promise();
} else {
    //Here it retries.. 
    setTimeout(function() {
        keepTrying();
    }, 500);
}
}
keepTrying();
df.done(function() {
//what to do after
});

Do you think there is an easier way to do it? I am working on Qualtrics so importing external libraries could be tricky when passing from one function to another.

Answer 1

I'd use an inner recursive function, and resolve the promise when the element is found.
You could add a count to that, and reject the promise after n tries etc.

function keepTrying() {

   var def = $.Deferred();

   (function rec() {
        var el  = document.getElementById('something');
        if ( el === null ) {
            setTimeout(rec, 500);
        } else {
            def.resolve();
        }
   })();
}

keepTrying().done(function() { ... });