Question

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 1

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.