Question

Watching a tutorial today I came across the following:

var q2Var1 = "hi there.",
    q2Var2 = String( "another string here." );

Is q2Var the “constructor notation” and q2Var the “literal notation” for declaring a variable, or am I not drawing the correct conclusion?

Thank you.

Answer 1

No, neither of those use a constructor to create a string object.

The first is just a string primitive, the second is a string primitive that is sent through the String conversion function, which will just return the string primitive unchanged.

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The String conversion function is usually used to turn other things into string primitives, for example a number:

var s = String(42);

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To create a String object you use the new keyword:

var s = new String("hi there.");

The String object has all the methods that you are used to use on a string, like the length property. The reason that you can use them on string primitives also, is that they are automatically converted to String objects when you use a method on them.

So, this:

var l = "asdf".length;

actually does the same as:

var l = new String("asdf").length;

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The String conversion function always returns a string primitive, so if you have a String object, the function will turn it back into a string primitive:

var s = "asdf"; // typeof s returns "string"

var s = new String(s); // typeof s now returns "object"

s = String(s); // typeof s now returns "string"