After a lot of time of searching what is the best way to synchronously load javascript from javascript I finally found a way to do it that works in almost any browser. The hardest part of it all is not loading and eval’ing the script, but allowing the script to set new variables in the global scope.

if (window.execScript) {
	window.execScript(contents);
} else {
	with (window) {
		window.eval(contents);
	}
}

This is what I’m finally using on my open source modular javascript project. To test it out I also found this website very useful. What I did was to create a test page that loaded a script, declared some global variables in different ways:

var someVariable = true;
someVariableWithoutVar = true;
eval("var someVariableWithEval = true");
eval("someVariableWithEvalWithoutVar = true");

Then loaded the website through browsershots and the results came in a few minutes. The tests passed on a lot of browsers including all versions I could test of Firefox, Opera, MSIE, Safari, with some minor exceptions: Safari 3.2.1 on Windows XP and OS X 10.5, Opera 7.54 on Windows XP, Konqueror 4.2 on Ubuntu 9.04.

The case with Safari 3.2.1 is that it cannot set global variables declared with var inside a eval’ed script. There’s a newer 3.2.3 version that I would like to test on to see if there is any difference. As for Opera, it’s an old version that nobody is probably using anymore. But for Konqueror I really don’t know the source of the error.

Take the test yourself. If you would like to see how the tests were done take a look at the sources here.

Update: The test suite now passes in almost every browser with the exception of some older versions of opera :).