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)

Note: String() can be called with or without new, but with different effects. See Return value.



Anything to be converted to a string.

Return value

When String is called as a constructor (with new), it creates a String object, which is not a primitive.

When String is called as a function, it coerces the parameter to a string primitive. Symbol values would be converted to "Symbol(description)", where description is the description of the Symbol, instead of throwing.

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.

Using String() to stringify a symbol

String() is the only case where a symbol can be converted to a string without throwing, because it's very explicit.

const sym = Symbol("example");
`${sym}`; // TypeError: Cannot convert a Symbol value to a string
"" + sym; // TypeError: Cannot convert a Symbol value to a string
"".concat(sym); // TypeError: Cannot convert a Symbol value to a string
const sym = Symbol("example");
String(sym); // "Symbol(example)"


ECMAScript Language Specification
# sec-string-constructor

Browser compatibility

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See also