JavaScript Tip: Running code in the dark

JavaScript Tip: Running code in the dark: "At a recent client, we were finding strange behaviour occuring in the JavaScript side of the house.

After taking a look, the problem was namespace collisions.

A couple of the developers were new to JavaScript, and didn’t know about the scoping world.

For example, the classic:


var foo = 'whee';


when placed at the top level of a script, and run in a browser, will actually set a variable on the scope that it is in, which is “window”.

You can simply test this with:


var foo = 'whee';
alert('foo = ' + foo);
alert('window.foo = ' + window.foo);


As such, the project was polluting the window object with everything under the sun, and there were conditions in which clashes occured.

We quickly fixed this with the lovely trick:


(function() {

// do you stuff here!

})();


You can make sure that the namespace is save with another simple example:


(function() {
var foo = 'whee';
alert('inside: ' + foo);
})();

alert('outside: ' + foo); // no var foo!
"