Question

I tried the following in JavaScript (Firefox 3.5, Windows XP):

(function(){
    window.foobar = 'Welcome!';
})();

var foobar = 'PWN3D!';

alert(foobar);

The output was ‘PWN3D!’. Why did my code PWN me? I thought var name = value; executed first.

Answer 1

From the specification (page 87):

A variable with an Initialiser is assigned the value of its AssignmentExpression when the VariableStatement is executed, not when the variable is created.

So the var causes the variable to be created first, but the value ('PWN3D!') is assigned to it in the normal execution order.