CODEWITHSUNDEEP
javascriptvariablesdeclaration
Rishabh
Rishabh

Reputation: 305

how does variable use before its declaration?

In Javascript how does variable used before definitions?

console.log("b ", b);

var b;

I want to understand how above statement work in javascript?

Upvotes: 1

Views: 1648

Answers (3)

Nisal Edu
Nisal Edu

Reputation: 7591

You can use d and then initialize d it will print undefined.
but if you use d with out any initialization it will return b is not defined Error . 

console.log("d",d);

   

 console.log("b "+b);
 var b = "What do you mean ?"    
 console.log("b ",b);

Upvotes: 0

guest271314
guest271314

Reputation: 1

b is undefined at code at Question. However, if b were a function, that variable declaration would be "hoisted" see 'Hoisted' JavaScript Variables and b would be defined within console.log() even where not actually defined until the next line.

console.log("b ", b);

function b() {}

Upvotes: 2

Niklesh Raut
Niklesh Raut

Reputation: 34914

JS first check how many variable and functions are going to use and variable are assigned as undefined and assigned at last.

So in the first example you can understand like var b = undefined and then console.log("b ", b); and then b=1; 

console.log("b ", b);
var b=1;

console.log("b ", b);

var b=1;
console.log("b ", b);

Upvotes: 1

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