What's the better practice: eval or append script?

javascript jquery dom eval
Kees C. Bakker picture Kees C. Bakker · Feb 3, 2012 · Viewed 12.6k times · Source

I need to execute a custom piece of JavaScript I got from some AJAX call. I could do an eval of the string or I could just append it in a script-tag to the DOM. Which method would be better?

var dynamicScript = 'alert(\'Hello world!\');';

Method 1 - Script:

var x = '<script type="text/javascript">' + dynamicScript  +'</scr' + 'ipt>';
$(document.body).append(x);

Method 2 - Eval:

eval(dynamicScript);

What method is better and why? Or is there an ever better alternative?

Answer

Rob W picture Rob W · Feb 3, 2012

I prefer eval, because it's generally faster than creating a script tag, and appending it (especially if you wanted to create and insert it using jQuery).

Side note (useful application of a script tag) I also use the script-tag-insertion method: In Google Chrome's extensions, injecting script-tags is the only way to run code in the scope of a page, because the window object is sandboxed.

PS. Notion of jQuery.getScript(). This method might be useful.

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