JavaScript

String Properties

Strings are immutable: Strings cannot be changed, only replaced. All string methods return a new string. They don't modify the original string.

String length

The length property returns the length of a string.

let text = "Kitten sings a song.";
let length = text.length;                // 20

String constructor

The constructor property returns the function that created the String prototype.

For strings, it returns: function String() { [native code] }.

let message = "Hello World!";
let text = message.constructor;
text;       // ƒ String() { [native code] }

String prototype

The prototype is a property available with all JavaScript objects. The prototype property allows you to add new properties and methods to strings.

Warning

• Only change the prototype of your own objects.
• Don't change prototype of an object we don't control.
• Don't change prototype of built in JS datatypes like numbers, strings, arrays, dates, booleans, function, and objects.

function Person(first, last, age, eyecolor) {
    this.firstName = first;
    this.lastName = last;
    this.eyeColor = eyecolor;
}
    
Person.prototype.nationality = "English";