When and why to use window before functions?

Question

There are numerous predefined Javascript functions that can be used with or without the object window as prefix. Example:

window.setTimeout(function() {

});

setTimeout(function() {

});

What is the rule for using this object before the functions? And what is the recommended way to work with it?

Answer 1

Javascript native functions (from the Browser) are part of the Object window and are global. This is the same as saying that the properties of window are accessible in the global scope. That is, they can be used in any scope.

However, they may be overwritten, and therefore no longer available within a certain scope/function. For example:

console.log(window.location.hostname); // pt.stackoverflow.com
(function () {
    var location = {};
    location.hostname= 'fooooo';
    console.log(location.hostname); // fooooo
    console.log(window.location.hostname); // pt.stackoverflow.com
})();

in this case window.location.pathname will access the property location of window. But if, within another scope, we declare a name variable pathname then in that scope, pathname will not be the same as window.pathname.

So, if necessary we can always access the "original" via window. The reason not to use window.pathname always is to save characters basically.