CODEWITHSUNDEEP
javascript
Abdallah Barghouti
Abdallah Barghouti

Reputation: 165

is it possible to define a global constant variable from inside a function in javascript?

I want to do something like this:

function defineGlobalConst(){
     const s = 10;
}

but I would like to access variable s from anywhere in my code, as I didn't type "const"

Upvotes: 1

Views: 1195

Answers (3)

Anthony Garcia-Labiad
Anthony Garcia-Labiad

Reputation: 3711

You can define a global variable like this:

In a browser:

function defineGlobalConst(){
     window.s = 10;
}

In node:

function defineGlobalConst(){
     global.s = 10;
}

If you want it to be a constant you could use defineProperty and a getter:

Object.defineProperty(window, "s", { 
  get: () => 10,
  set: () => { throw TypeError('Assignment to constant variable.') },
});

Upvotes: 9

code-gorilla
code-gorilla

Reputation: 2408

Your only option is to store the value in the window. Just be sure to at least namespace your value, as it could conflict with something else already in the window:

// Create the namespace at the beginning of your program.
if (!window.MY_APP) {
  window.MY_APP = {};
}

window.MY_APP.s = 10;

Upvotes: 1

Scott Marcus
Scott Marcus

Reputation: 65808

It is possible to solve your problem by utilizing an anti-pattern. Be advised that I'm not advocating this approach, but from a pure "can you do it" perspective, any non-declared variable that is assigned in a function becomes a Global by default (of course this does not create a constant as you've asked, but thought I would show it anyway):

function foo(){
  bar = "baz";   // implicit Global;
}

foo();


// Show that "bar" was, in fact added to "window"
console.log(window.bar);  // "baz"
console.log(bar);  // "baz"

Upvotes: -2

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