• In JavaScript, non-primitive data types are more complex and mutable data structures compared to primitive types. They can store collections of data or more complicated entities. The main non-primitive data types in JavaScript include Objects, Arrays, Functions, and others like Maps, Sets, etc. All non-primitive types in JavaScript are essentially objects, which means they are reference types.

Objects

• An object is a collection of properties, and each property is associated with a name (key) and a value.

• Key Characteristics

  • Dynamic structure: Objects can be created with any number of properties, and properties can be added, modified, or deleted.
  • Key-value pairs: Keys are usually strings (though they can be symbols) and values can be of any data type.

  let person = {
    name: "Alice",
    age: 25,
    isStudent: true,
    greet: function() {
      console.log("Hello, " + this.name);
    }
  };
  
  console.log(person.name);  // Output: Alice
  person.greet();  // Output: Hello, Alice
  

• Accessing Object Properties

  • Dot notation: person.name
  • Bracket notation: person['age']

• Key Methods for Object Manipulation:

  • Object.keys(obj): Returns an array of the object’s property names (keys).
  • Object.values(obj): Returns an array of the object’s property values.
  • Object.entries(obj): Returns an array of the object's key-value pairs.

• Nested Objects:

  • Objects can have other objects as their property values.

  let car = {
    make: "Toyota",
    model: "Corolla",
    engine: {
      type: "V4",
      horsepower: 130
    }
  };
  
  console.log(car.engine.horsepower);  // Output: 130
  

Arrays

• Arrays are special objects designed to store sequences of values. They are a type of list-like object and are one of the most common data structures.

• Key Characteristics:

  • Index-based: Each element in an array has an index starting from 0.
  • Dynamic: You can dynamically add or remove elements.
  • Heterogeneous: An array can store values of different types (numbers, strings, objects, etc.).

  let colors = ["Red", "Green", "Blue"];
  console.log(colors[1]);  // Output: Green
  
  // Adding a new element
  colors.push("Yellow");
  console.log(colors);  // Output: ["Red", "Green", "Blue", "Yellow"]
  

• Array Methods

  • push(): Adds an element to the end of the array.
  • pop(): Removes the last element of the array.
  • shift(): Removes the first element of the array.
  • unshift(): Adds one or more elements to the beginning of the array.
  • forEach(): Iterates over each array element.
  • map(): Creates a new array with the results of calling a provided function on every element in the array.

• Multidimensional Arrays:

  • Arrays can contain other arrays as elements, creating a multidimensional array.

  let matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
  ];
  
  console.log(matrix[1][2]);  // Output: 6
  
  

Functions

• Functions are a type of object that can be invoked to perform an action. In JavaScript, functions are first-class citizens, which means they can be treated as data.

• Key Characteristics:

  • Reusable: Functions encapsulate code logic that can be reused multiple times.
  • First-class functions: Functions can be assigned to variables, passed as arguments to other functions, and returned from functions.

  function greet(name) {
    return "Hello, " + name;
  }
  
  let message = greet("Alice");
  console.log(message);  // Output: Hello, Alice
  

• Functions as Values

  • Functions can be stored in variables and passed as arguments.

  let add = function(a, b) {
    return a + b;
  };
  
  console.log(add(5, 3));  // Output: 8
  

• Anonymous Functions and Arrow Functions

  • Arrow functions offer a more concise syntax:

  let multiply = (x, y) => x * y;
  console.log(multiply(4, 5));  // Output: 20
  

Dates

• The Date object is used to work with dates and times in JavaScript.

  let now = new Date();
  console.log(now);  // Output: Current date and time
  
  // Specific date
  let birthday = new Date('1990-05-15');
  console.log(birthday);  // Output: Tue May 15 1990