String.prototype.toString()

A string representing the specified string value.

The String object overrides the toString method of Object; it does not inherit Object.prototype.toString(). For String values, the toString method returns the string itself (if it's a primitive) or the string that the String object wraps. It has the exact same implementation as String.prototype.valueOf().

The toString() method requires its this value to be a String primitive or wrapper object. It throws a TypeError for other this values without attempting to coerce them to string values.

Because String doesn't have a [@@toPrimitive]() method, JavaScript calls the toString() method automatically when a String object is used in a context expecting a string, such as in a template literal. However, String primitive values do not consult the toString() method to be coerced to strings — since they are already strings, no conversion is performed.

String.prototype.toString = () => "Overridden";
console.log(`${"foo"}`); // "foo"
console.log(`${new String("foo")}`); // "Overridden"

The following example displays the string value of a String object:

const x = new String("Hello world");

console.log(x.toString()); // "Hello world"

• String.prototype.valueOf()