Should I use window.variable or var?

We have a lot of setup JS code that defines panels, buttons, etc that will be used in many other JS files.

Typically, we do something like:

grid.js

var myGrid = .....

combos.js

var myCombo = .....

Then, in our application code, we:

application.js

function blah() {
    myGrid.someMethod()
}

someother.js

function foo() {
    myCombo.someMethod();
    myGrid.someMethod();
}

So, should we be using the var myGrid or is better to use window.myGrid

What's the difference?

---

I would suggest creating a namespace variable var App = {};

App.myGrid = ...

That way you can limit the pollution of the global namespace.

EDIT: Regarding the number of variables issue - 2 possible solutions come to mind:

You can further namespace them by type(Grids, Buttons, etc) or by relationship(ClientInfoSection, AddressSection, etc)

You encapsulate your methods in objects that get instantiated with the components you have

ex: you have

function foo() {
    myCombo.someMethod();
    myGrid.someMethod();
}

becomes:

var Foo = function(combo, grid) {
    var myCombo = combo;//will be a private property
    this.myGrid = grid;//will be a public property
    this.foo = function() {//public method
        myCombo.someMethod();
        myGrid.someMethod();
    }
}
App.myFoo = new Foo(someCombo, someGrid);
App.myFoo.foo();

this way you limit the amount of little objects and only expose what you need (namely the foo function)

PS: if you need to expose the internal components then add them to this inside the constructor function

---

功能上潜在的重要区别是window.myGrid可以被delete ，而var myGrid不能。

var test1 = 'value';
window.test2 = 'value';


console.log( delete window.test1 ); // false ( was not deleted )
console.log( delete window.test2 ); // true  ( was deleted )


console.log( test1 );  // 'value'         ( still accessible )
console.log( test2 );  // ReferenceError  ( no longer exists )

---

One nice use of window.variable is that you can check it without having a javascript error. For example, if you have:

if (myVar) {
    //do work
}

and myVar is not defined anywhere on the page, you will get a javascript error. However:

if (window.myVar) {
    //do work
}

gives no error, and works as one would expect.

var myVar = 'test' and window.myVar = 'test' are roughly equivalent.

Aside from that, as other said, you should descend from one global object to avoid polluting the global namespace.

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