Javascript executing when jQuery not ready

Question

The following scenario is a problem I am having. I came to the conclusion that jQuery must not be ready when Javascript is executing by observing this scenario.

Scenario:

I have a Java application which injects Javascript script tags into the currently loaded DOM page. The following Java code runs inline Javascript which inserts jquery.js and myCode.js. myCode.js holds my Javascript codes.

 browser.executeJavaScript("var head= document.getElementsByTagName('head')[0];" +
                                "var script= document.createElement('script');script.type= 'text/javascript';script.src= 'jquery.js';head.appendChild(script);" +
                                "var script4= document.createElement('script');script4.type= 'text/javascript';script4.src= 'http://myCode.js';head.appendChild(script4);");

In this Java application, I also have a buttonListener that fires a function in myCode.js in ActionPerformed();

executedJS = browser.executeJavaScript("replaceAllLinks()");

The problem that is encountered is nullPointerException at the above line when button is clicked. Accomodating for null case results in endless loop without any changes.

while(executedJS == null) browser.executeJavaScript("replaceAllLinks()");

The cause of the problem was pinpointed down to when jQuery functions, methods are present inside replaceAllLinks(); javascript function. when jQuery, methods were absent, no problems could be observed. There was not one instance of nullPointerException raised.

The only possible underlying issue would be that somehow jQuery library is not fully loaded while replaceAllLinks(); is being executed. If jQuery methods and functions were not in use, it doesn't matter and everything runs okay.

My question is then, how can I make sure that jQuery is fully loaded and available for use?

Where is your $(document).ready ?

jamesmortensen
– jamesmortensen

2011-01-22 08:56:18 +00:00
Commented Jan 22, 2011 at 8:56 — jamesmortensen
– jamesmortensen, Commented Jan 22, 2011 at 8:56

Sheavi · Accepted Answer · 2011-01-22 09:07:14Z

1

Every script relying on jQuery should be contained inside a DOM ready function. Such a function normally takes this form:

$(document).ready(function() {
    /* code here */
});

and a shortcut to achieve the same thing would be:

$(function() {
    /* code here */
});

Here's the documentation for further information on the ready method: http://api.jquery.com/ready/

answered Jan 22, 2011 at 9:07

Sheavi

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Comments

Dr.Molle · Accepted Answer · 2011-01-22 10:56:33Z

0

Declare some global variable at the end jquery.js, e.g.

window.jQueryIsLoaded=true;

and check this variable before using jQuery.

<edit>Forget this, see Salman A's comment below, should be the right answer.</edit>

edited Jan 22, 2011 at 10:56

answered Jan 22, 2011 at 10:33

Dr.Molle

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4 Comments

Salman Arshad Over a year ago

Infact, you can just check for typeof jQuery !== 'undefined'.

Dr.Molle Over a year ago

But how sure are you that jQuery is completely downloaded in this case?

Dr.Molle Over a year ago

OK, I took a look at jquery.js, has to be complete if jQuery is known.

KJW Over a year ago

what's weird is that jQuery is fully loaded....but the problem still occurs....so I was wrong ?

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