String() constructor

The String constructor is used to create a new String object. When called instead as a function, it performs type conversion to a primitive string, which is usually more useful.


new String(thing)



Anything to be converted to a string.


When String is called as a function, it coerces the parameter to a string primitive. When String is called as a constructor (with new), it creates a String object, which is not a primitive.

Warning: You should rarely find yourself using String as a constructor.


String constructor and String function

String function and String constructor produce different results:

const a = new String("Hello world"); // a === "Hello world" is false
const b = String("Hello world");     // b === "Hello world" is true
a instanceof String;         // is true
b instanceof String;         // is false
typeof a // "object"
typeof b // "string"

Here, the function produces a string (the primitive type) as promised. However, the constructor produces an instance of the type String (an object wrapper) and that's why you rarely want to use the String constructor at all.


ECMAScript Language Specification
# sec-string-constructor

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See also