Question

I have a simple javascript class.

One method of this class sets up a timer using setInterval function. The method that I want to call every time the event fires is defined inside the same class.

The question is, how can I pass this method as a parameter to the setInterval function?

One attempt was setInterval(‘this.showLoading(), 100). But doesn’t work. This method access class properties, so I need the ‘this’ reference.

This is the sample code:

    function LoadingPicture(Id)
    {
        this.imgArray = null;
        this.currentImg = 0;
        this.elementId = Id;
        this.loadingTimer = null;
    }


   LoadingPicture.prototype.showLoading = function()
    {
        if(this.currentImg == imgArray.length)
            currentImg = 0;

        document.getElementById(this.elementId).src = imgArray[this.currentImg++].src;
    }


    LoadingPicture.prototype.StartLoading = function()
    {
        document.getElementById(this.elementId).style.visibility = "visible";
        loadingTimer = setInterval("showLoading()", 100);
    }

Answer 1

setInterval can take a function directly, not just a string.
https://developer.mozilla.org/en/DOM/window.setInterval

i.e.

loadingTimer = setInterval(showLoading, 100);

But, for optimal browser compatibility, you should use a closure with an explicit reference:

 var t = this;
 loadingTimer = setInterval(function(){t.showLoading();}, 100);