CODEWITHSUNDEEP
javascript
user5543457
user5543457

Reputation:

What does "= +" do in JavaScript?

Was reading through Douglas Crockford's code here and saw a line 

var value = +node.getValue();

but I don't see anything at http://www.w3schools.com/js/js_operators.asp which corresponds to an = + or a way that + can be used as a unary operator. So what does this mean?

Upvotes: 3

Views: 87

Answers (3)

user2157249
user2157249

Reputation: 31

Just to add on to what's been said do the following:

var a = +'4';
var b = '4';

console.log(typeof(a));//Number
console.log(typeof(b));//String

Upvotes: 0

Sterling Bourne
Sterling Bourne

Reputation: 3342

It's just a quick way to make sure the variable is an INT, (vs. a STR or BOOL, e.g.).

Upvotes: 0

ssube
ssube

Reputation: 48257

The - and + operators are both unary in JS and, before forcing the value's sign, must convert the value to a number.

Obviously - will convert to a number and invert the sign, but + only does the first part. Running +"100" will return the number 100.

This behavior is explicitly stated in the spec at 11.4.6, where the unary + operator is defined:

The unary + operator converts its operand to Number type.

Upvotes: 7

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