CODEWITHSUNDEEP
javascriptjshint
user2413333
user2413333

Reputation: 1405

Why is Jshint saying "variable already defined" in this if statement?

I have this code:

 if ( something is true ) {
        var someVar = true;
    } else {
       var someVar = false;
    }

JsHint is saying that "someVar was already defined" on the else statement part. Why is this and how do I fix it?

Thanks

Upvotes: 59

Views: 16457

Answers (3)

Alnitak
Alnitak

Reputation: 339916

JS variables do not have block scope, they have "function" scope (or sometimes global).

The declaration (but not the assignment) is "hoisted" to the top of the function.

jshint is warning you that you have two such declarations - your code is equivalent to:

var someVar;
var someVar;  // warning!
if (something) {
     someVar = true;
} else {
     someVar = false;
}

Upvotes: 80

Erik Christianson
Erik Christianson

Reputation: 507

This is due to hoisting.

In javascript, no matter where you define a new variable with var, it moves it to the top of the function you are in. Your code is producing the following above your if block at the top of the function:

var someVar;
var someVar;

Here is a tutorial to explain hoisting:

http://net.tutsplus.com/tutorials/javascript-ajax/quick-tip-javascript-hoisting-explained/

Upvotes: 21

Pointy
Pointy

Reputation: 413828

You shouldn't put var declarations in such places. Put the var declaration before the if, and then just set "someVar" to a value.

Indeed, here you don't need an if statement at all:

var someVar = !!(something);

will do the same thing. (The double application of ! ensures that "someVar" is set to either true or false, based on the "truthiness" of something.)

Upvotes: 13

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