How to global a js var in a function?

Question

It is possible to global a variable inside a function, if not, how can I access a var in function b from function a.

var money;
var moneyInput = document.getElementById('input');

function check(){
if (moneyInput.value == "") {
    money = 100;
}                   

function hit() {
    document.write(money) // will this money var be 100 or undefined?
}

*"It is possible to global a variable inside a function"* Yes. *"how can I access a var in function b from function a"* You usually pass the value as argument to the function. Having to use global variables could be an indicator of bad design. Can you provide more information/context about what you are actually trying to do? — Felix Kling, Jun 03 '17 at 17:12
Also please use the search because this is a possible duplicate of [How to declare a global variable in JavaScript?](https://stackoverflow.com/q/3352020/218196) — Felix Kling, Jun 03 '17 at 17:13
Possible duplicate of [How to declare a global variable in JavaScript?](https://stackoverflow.com/questions/3352020/how-to-declare-a-global-variable-in-javascript) — Assafi Cohen-Arazi, Jun 03 '17 at 17:15

score 2 · Answer 1 · edited Jun 20 '20 at 09:12

Just declare that variable outside function and then use it inside of that function.

P.S Please, post some code that you tried already.

let a = 5;
let b = 0; // Declare global variable

function printAB(_b) {
  b = _b; // Set new value through this function
  console.log(a, b);
}

function printBC() {
  let c = 7;
  console.log(b, c); // Get b variable
}

printBC(); // 0, 7 // b = 0
printAB(2); // 5, 2
printBC(); // 2, 7 // b = 2

Edit

With code you provided, answer is simple. Variable money can be equal 100 or be undefined, that depends if function hit will be called before function check.

So did I. Check it and mark as answered if that's what you wanted to know. — Oen44, Jun 03 '17 at 21:18

score 1 · Answer 2 · answered Jun 03 '17 at 17:07

1

If you assign a value to an undeclared variable in a function it will be created as a global variable.

answered Jun 03 '17 at 17:07

user2182349

9,569
3
29
41

score 1 · Answer 3 · answered Jun 03 '17 at 17:07

You should declare the variable outside of the function scope:

var myGlobalVar = "foo";

function a(){
   var myLocalVar = 'bar';
   alert(myGlobalVar); //shows foo
   alert(myLocalVar); //shows bar
}

function b(){
   var myLocalVar = 'baz';
   alert(myGlobalVar); //shows foo too
   alert(myLocalVar); //shows baz
}

score 1 · Answer 4 · answered Jun 03 '17 at 17:08

1

Assign a variable without using var, let, or const

var foo = 'bar';

function fn() {
  console.log(foo);
  bar = 'xyz';
}

fn()

console.log(bar)

Repl: https://repl.it/languages/javascript

answered Jun 03 '17 at 17:08

Baruch

2,381
1
17
29

score 1 · Answer 5 · answered Jun 03 '17 at 17:09

1

You can assign a value to the global object ( window in browsers):

function a(){
  window.test="test";
}
function b(){
 console.log(test);
}
a(),b();

answered Jun 03 '17 at 17:09

Jonas Wilms

132,000
20
149
151

score 1 · Answer 6 · answered Jun 03 '17 at 17:10

Declaring the variable on the outer scope and using it inside should solve your problem. However if you insist on creating a variable on the global scope you can do the following;

window.VAR_NAME = 'foo';

By doing so you are actually creating a global variable VAR_NAME and it now has the value foo.

score 1 · Answer 7 · answered Jun 03 '17 at 17:19

/* 1 */

var a = 'sample text';

function one() {
  a = 'modified text';
}

function two() {
  console.log(a);
}

one();
two();

/* 2 */

function one(callback) {
  var a = 'sample text callback';
  callback(a);
}

function two() {
  one(function(a) {
    console.log(a);
  });
}

two();

/* 3 */

var one = new Promise(function(resolve, reject) {
  var a = 'sample text promise';
  resolve(a);
});

function two() {
  one.then(function(a) {
    console.log(a);
  });
}

two();

/* 4 */

var myGlobals = {};

function one() {
  myGlobals.a = 'sample text';
}

function two() {
  console.log(myGlobals.a);
}

one();
two();

How to global a js var in a function?

7 Answers7

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