What's the point of new String(“x”) in JavaScript?

Question

What are the use cases for doing new String(\"already a string\")?

What\'s the whole point of it?

Answer 1

In most cases you work alone and can control yourself, or on a team and there is a team guideline, or can see the code you're working with, so it shouldn't be a problem. But you can always be extra safe:

var obj = new String("something");
typeof obj; // "object"

obj = ""+obj;
typeof obj; // "string"

Update

Haven't though much about the implications of this, although it seems to work:

var obj = new String("something"), obj2 = "something else";
obj.constructor === String; // true
obj2.constructor === String; // true

Of course, you should check if the object has a constructor (i.e. if it is an object).

So you could have:

isString(obj) {
   return typeof obj === "string" || typeof obj === "object" && obj.constructor === String;
}

Although I suggest you just use typeof and "string", a user should know to pass through a normal string literal.

I should note this method is probably susceptible to someone creating an object and setting it's constructor to be String (which would indeed be completely obscure), even though it isn't a string...