Javascript synchronous timeout in while loop

Question

I am trying to fake synchronous JavaScript while doing an AJAX request. I have an getPagePath(id) function that needs to get the page path of an page by giving it an page ID, it receives the data trough an web API. I thought this was going to be simple, just do an ajax request to the server and receive the page path. But what is happening: when requesting the page path my code keeps running and returns an empty var, after that the ajax call finishes, but to late.

I know my explaining is not much saying so here is my code:

var getPagePath = function() {

    // Function to check if this.pagePath is set.
    var pagePathReady = function() {
        console.log('PAGEPATH: CHECKING');
        if (this.pagePath && this.pagePath != null) {
            return true;
        } else {
            return false;
        }
    };

    if (!pagePathReady()) {
        // No pagePath defined so lets set it.
        this._setPagePath();

        while (!pagePathReady())
        {
            // Not yet defined, check again..

            // *** The problem ***
            // This while loop is running insanely fast making the browser crash.
            // How can I make this wile loop pause for 1 sec?
            // *******************

            console.log('PAGEPATH: NOT READY -> CHECK AGAIN');
        }

        // READY
        console.log('PAGEPATH: READY -> VALUE: ' + this.pagePath);
        return this.pagePath;
    } else {
        return this.pagePath;
    }
};

var _setPagePath = function() {
    if (!this.pagePathRequestFired) {
        this.pagePathRequestFired = true;
        // Fire request.
        system.url(
            this.getNodeId(), 
            function(url) {
                // Request ready, set pagePath.
                this.pagePath = url;
                this.pagePathRequestFired = false;
            }, 
            this
        );
    } else {
        // Call already running..
    }
};

I have set the problem in the more explaining comments.

Thanks in advance!

goat · Accepted Answer · 2012-06-19 15:31:51Z

1

You can make an ajax call synchronous if you really need to.

xmlhttp.open("GET", "url", false);

Note the 3rd param.

But, I think you just need more practice in writing your code to work with the event/callback concept.

answered Jun 19, 2012 at 15:31

goat

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Comments

Jason Kulatunga · Accepted Answer · 2012-06-19 14:44:47Z

1

Instead of polling the pagePath (which doesn't seem to be required IMHO) why not just execute a callback when the _setPagePath is ready? If you want to fake a synchronous request, you can just display a loading spinner to the user as an overlay, disabling the UI.

answered Jun 19, 2012 at 14:44

Jason Kulatunga

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2 Comments

mmmmm Over a year ago

I use this approach cause in need to set the pagePath in an other piece of code, I set it like paramBag.path = this.controller.getPagePath();

mmmmm Over a year ago

In addition to the above comment: I use this approach cause in need to set the pagePath in an other piece of code, I set it like paramBag.path = this.controller.getPagePath(); When working with callbacks the getPagePath() will return undefined while the request is still running. When the request is ready it will call the callback, but the callback is not able to set the property in the paramBag. Sorry, I know things don't sound relay clear. Having a hard time explaining this situation..

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