what is this code doing?

[Reza Razavipour]

function Param(stringifiedValue) {

    if (!this instanceof Param) {

        return new Param(stringifiedValue);

    }

    this.value = stringifiedValue;

}

Is this only doing away with the user having to do a new?

Can someone explain?

[mscdex]

On Thursday, September 11, 2014 5:41:15 PM UTC-4, Reza Razavipour wrote:

Is this only doing away with the user having to do a new?

You're correct, although it's usually `if (!(this instanceof Param))` instead of `if (!this instanceof Param)` for clarity.

[Aria Stewart]

Exactly that.

[Ryan Graham]

That is probably what the author intended, yes.

However, ! has higher precedence than instanceof, so it is actually broken.

It should be "if (!(this instanceof Param))" for the (likely) desired effect.

~Ryan

--
http://twitter.com/rmgraham

[Ryan Schmidt]

Yes. If a consumer of this code writes "var p = Param()" instead of "var p = new Param()", the above instanceof check will make things still work right. Without that code, "var p = Param()" will silently fail to work in the expected manner.

Some more on this topic:

http://stackoverflow.com/a/383503/951159