When I set the onload property I use
window.onload=initialize_page;
However, when I use undefined, which I understand is a window property I simply use:
undefined
How do I know when to scope properties?
If I remove window from the first statement it works. I guess I've seen both in code here on SO, but which way is best practice?
When you want to define a global variable, it's recommended to prefix window.
, to prevent conflicts with local variables with the same name.
For example, Rocket (at the OP's comments) suggested to use onload=initialize_page;
instead of window.onload = ...
. This will fail in the following case:
function foo() {
var onload = "on load";
onload = initialise_page;
// What? Let's check:
alert(onload === window.onload); //false
}
foo();
If you encounter a variable, and don't know whether it's a global variable or not, you can use the following code to determine it:
alert( 'somevar' in window ); //If true, then in global scope. If false, then not
alert( somevar === window.somevar); // Risky. If somevar is not an object, this
// comparison will also be true. Example:
// var local = 1;window.local=1;
// ^ They're equal by value
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