How can I execute Javascript via ExtJS AJAX call without eval() as I can with JQuery?

Question

I would like to execute javascript in pages which I load via Ext.Ajax.request. To do this, I have to load the scripts and eval() them like this:

Ext.Ajax.request({
    url: 'content/view_application.php',
    success: function(objServerResponse) {
        var responseText = objServerResponse.responseText;
        regionContent.update(responseText);
        var scripts, scriptsFinder=/<script[^>]*>([\s\S]+)<\/script>/gi;
        while(scripts=scriptsFinder.exec(responseText)) {
            eval(scripts[1]);
        }
    }
});

With JQuery, however, I can have Javascript executed in pages which are called via AJAX without resorting to eval() like this:

function replaceContentOnClick(id, pageToLoad) {
    $('body').delegate(('#' + id), 'click', function(){
        $.get('content/' + pageToLoad, function(data) {
            $('#regionContent .x-panel-body').html(data);
        });
    });
}

How is it that JQuery manages to execute the javascript in the loaded page without eval()? Is there a way to load the javascript without resorting to eval() in ExtJS as well?

I can answer only your first question: jquery looks at the Content-Type http header and if it is application/json it will do the necessary conversion before invoking the success callback. — Darin Dimitrov
– Darin Dimitrov, Commented Dec 2, 2010 at 10:54

Mutation Person · Accepted Answer · 2010-12-02 11:08:48Z

3

Personally, I wouldn't worry about the eval statement. I am aware that Douglas Crockford counsels against its use:

eval is evil

The eval function (and its relatives, Function, setTimeout, and setInterval) provide access to the JavaScript compiler. This is sometimes necessary, but in most cases it indicates the presence of extremely bad coding. The eval function is the most misused feature of JavaScript.

(from http://www.jslint.com/lint.html)

Here he states that "This is sometimes necessary", and I would argue that your use is a valid one.

The JSON2.js library (http://www.json.org) uses this command, and flags to JSLint that this is intended:

/*jslint evil: true */

Is there a particular reason that you would like to avoid its use?

answered Dec 2, 2010 at 11:08

Mutation Person

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2 Comments

Nathan Over a year ago

+1, I agree (and very nearly wrote an answer similar to yours), but the advantage of my solution (well, jQuery's solution) is that it executes the statement in the global context, which eval doesn't do. (In many situations local is better, but I would think that for downloading scripts via AJAX, the solution nearly always needs to be global.)

Edward Tanguay Over a year ago

I would like to avoid its use simply because it raises a security issue, and as you mentioned, Douglas Crockford identified it as a "bad part" of Javascript for this reason. I also assumed that executing javascript from within an AJAX call would be taken care of by other methods so that it is safer than calling a raw eval on script that was loaded from any source.

Nathan · Accepted Answer · 2010-12-02 10:59:21Z

1

Well, go to the jQuery source (http://code.jquery.com/jquery-latest.js) and Ctrl+F for globalEval: function. This is the function which runs JavaScript. You'll see it actually adds script tags into the DOM. As for extJS, I don't know. Try searching in their source code for "script" or 'script' to see if they insert script tags anywhere in a similar way. Or you could just implement your own globalEval.

answered Dec 2, 2010 at 10:59

Nathan

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Comments

Community · Accepted Answer · 2017-05-23 10:33:06Z

1

At the risk of sounding like a broken record, please see my other answer regarding the loadScripts config. You should consider sticking to the same question when it's just a follow-up to what you've already asked, rather than starting brand new questions.

edited May 23, 2017 at 10:33

CommunityBot

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answered Dec 2, 2010 at 16:01

Brian Moeskau

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