Unable to access global variable in javascript - Stack Overflow

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As per me, every variable declared in javascript above functions treat as global. But in my case, i unable to access that variable show undefined. Here is jsfiddle

code:

__getUserByRmId('sun1')
var firstCallFlag = 1;
function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}

As per me, every variable declared in javascript above functions treat as global. But in my case, i unable to access that variable show undefined. Here is jsfiddle

code:

__getUserByRmId('sun1')
var firstCallFlag = 1;
function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}

• javascript

Share Improve this question Follow asked Jan 17, 2017 at 6:28 user7104874user7104874 1,38133 gold badges1616 silver badges2121 bronze badges

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5 Answers 5

Sorted by: Reset to default 3

This is because the variable is defined after the function is called.

You can do this. It will work.

var firstCallFlag = 1;
__getUserByRmId('sun1')

function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}

By the way, hoisting is JavaScript's default behavior of moving all declarations to the top of the current scope. So, something like this should work.

 firstCallFlag =1 ;
__getUserByRmId('sun1')

function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}
var firstCallFlag;

However, JavaScript Initializations are Not Hoisted. Thus, the code like below will consider the variable firstCallFlag undefined.

__getUserByRmId('sun1')

function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}
var firstCallFlag = 1; 

There is a term function and variable hoisting. When you create a function like that and a variable with var, they moved to the top of of all. But the functions are hoisted first before variables. So when you call the function, it sees the function , but doesn't see the variable.

Engine parses your code to this and executes line by line. So it doesn't see the variable.

function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}

__getUserByRmId('sun1')

var firstCallFlag = 1;

You need to call your function after the variable declaration

var firstCallFlag = 1;

__getUserByRmId('sun1');

function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}        

Call the function after declaring the variable. Function will hoist first and then the variables.

var firstCallFlag = 1;
function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}
__getUserByRmId('sun1');

If you still want to work with the same pattern of approach without declaring the variable on top of function call, then you should have a timeout call like this:

_getUserByRmId('sun1');

var firstCallFlag = 1;

function __getUserByRmId(rmId) {
   setTimeout(function(){
      console.log(firstCallFlag); 
   },1);        
}

var firstCallFlag = 1;
function __getUserByRmId(rmId) {
    console.log(firstCallFlag); 
}
__getUserByRmId('sun1');

Its beacuse you have to define the variable "firstCallFlag " first and then call the function __getUserByRmId('sun1');....variable hoisting in javascript

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