Javascript: Creating string by different methods

Question

On Firebug:

>>> str1 = String('String One');
"String One"
typeof(str1);
"string"
>>> str2 = new String('String Two');
String { 0="S", 1="t", 2="r", more...}
typeof(str2);
"object"

My Question is what is the difference between both technique?
What is the advantage of one over the other?

• Rob W: Have a look at developer.mozilla.org/en/JavaScript/Reference/Global_Objects/….

Answer 1

The only real difference is that using new String(), you get an object that extends from Object, meaning that this code works:

var foo = new String( 'bar' );
foo.property = 42;

whereas this doesn't:

var foo = 'bar';
foo.property = 42;

It's also sometimes useful if you need to get a string:

var foo = new String( 21*2 );

Answer 2

There really isn't much of an advantage one way or the other because almost nobody creates a string this way they just declare var a = 'This is a string'; This is similar to the fact that the accepted way to create an array is not var a = new Array() but var a = []. I guess the first way might have an advantage because it labeled as a string instead of an object, but

var a = 'This is a string';
typeof(a);//returns string

• david: i dont know using square brackets as the array constructor is accepted over new Array(), it just easer :}

Answer 3

in the first example you got the return type of String();
in the second you got the type of String() itself / or more precisely the type of the new String() instance.

more info:
http://www.w3schools.com/jsref/jsref_String.asp
http://www.w3schools.com/jsref/jsref_obj_string.asp

• hugomg: eww, don't like to w3schools bro

Answer 4

The new String wrapper is a wart put into the language a long time ago to please the Java folks. As you might have already noticed, those inconsistencies are good reasons why it is not a widely recommended practice today.

Meanwhile, using String(something) is useful if you want to convert values to strings but most people just use the shorter ''+something instead.

String('string') is unecessary, since 'string' already is a string.

tldr avoid new String and other wrappers like new Array and new Number like the plague.