Turn a JavaScript local variable into a global variable

Question

I have a JavaScript function to generate a variable. That function is activated by an onclick button event.

After that variable is generated, I need to use it as a global variable so that other JavaScript processes can use that variable.

How do I do it?

FYI,let alone processes, javascript don't even use threads except i think setTimeout — Srinivas Reddy Thatiparthy, May 07 '10 at 11:31

score 13 · Accepted Answer · edited May 23 '17 at 12:17

13

You should be able to add the variable's value to a property of the global window object:

window.yourVarName = yourVarName;

Then the other functions will be able to access yourVarName simply by referencing yourVarname directly. There will be no need to use window.yourVarName.

However keep in mind that in general, global variables are evil.

edited May 23 '17 at 12:17

Community

1
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answered May 07 '10 at 11:30

Daniel Vassallo

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why is it evil? Mind explain a little? – Eric Sim May 07 '10 at 11:32
@Eric: http://stackoverflow.com/questions/2613310/ive-heard-global-variables-are-bad-what-alternative-solution-should-i-use – Daniel Vassallo May 07 '10 at 11:33
in Javascript, by default it is windows object,why again prefixing it with window – Srinivas Reddy Thatiparthy May 07 '10 at 11:33
@Srinivas: Primarily clarity, to avoid the horror of implicit globals. – T.J. Crowder May 07 '10 at 11:35
@Srinivas makes the assignment clearer, not including it would make it ambiguous were that variable is declared. – roryf May 07 '10 at 11:35
@Srinivas: Because if I understood the OP's context correctly, the variable `yourVarname` will be defined in local function scope as well. – Daniel Vassallo May 07 '10 at 11:36
If you assign a variable inside local function scope without the `var` keyword, it gets assigned to the window object (in FF at least) so the behaviour is the same. – roryf May 07 '10 at 13:00
@roryf: Yes true. But I think the OP had it as a local variable. It could be a function argument for example. – Daniel Vassallo May 07 '10 at 13:23

score 3 · Answer 2 · edited Oct 15 '20 at 19:45

Declare the variable outside the scope of the function:

var foo = null;

function myClickEvent() {
    foo = someStuffThatGetsValue;
}

Better yet, use a single global variable as the namespace ("MyApp") for your application, and store the value inside that:

var MyApp = {
    foo: null
};

function myClickEvent() {
    MyApp.foo = someStuffThatGetsValue;
}

The function itself could even be included in there.

Turn a JavaScript local variable into a global variable

2 Answers2

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