JavaScript Non-Primitive Data Types

JavaScript Non-Primitive Data Types

Arrays

• Definition: Ordered collections of values that can hold multiple items.
• Creation:
  • Using array literals: let arr = [1, 2, 3];
  • Using the Array constructor: let arr = new Array(1, 2, 3);
• Key Characteristics:
  • Can hold different data types (numbers, strings, objects, etc.).
  • Dynamic size: Can change in size (e.g., push, pop).
• Common Methods:
  • .push(): Adds an item to the end.
  • .pop(): Removes the last item.
  • .shift(): Removes the first item.
  • .unshift(): Adds an item to the front.
  • .slice(): Returns a portion of the array.
  • .map(): Creates a new array based on the results of a function.
  • .filter(): Creates a new array with elements that pass a test.

Objects

• Definition: Collections of key-value pairs, where keys are strings and values can be any data type.
• Creation:
  • Using object literals: let obj = {key1: value1, key2: value2};
  • Using the Object constructor: let obj = new Object();
• Key Characteristics:
  • Keys can be any valid string (or Symbol).
  • Can store functions as values (methods).
  • Properties can be accessed using dot notation (obj.key1) or bracket notation (obj['key1']).
• Common Methods:
  • Object.keys(): Returns an array of keys.
  • Object.values(): Returns an array of values.
  • Object.entries(): Returns an array of [key, value] pairs.
  • Object.assign(): Copies values from one or more source objects to a target object.

Functions

• Definition: First-class objects that can be assigned to variables, passed as arguments, or returned from other functions.
• Creation:
  • Function declaration: function myFunction() { /*...*/ }
  • Function expression: let myFunction = function() { /*...*/ };
  • Arrow functions: let myFunction = () => { /*...*/ };
• Key Characteristics:
  • Can return a value using the return statement.
  • Can have parameters and arguments.
  • Can be called repeatedly.
  • Can be used as a method within objects.
• Common Concepts:
  • Scope: Functions create their own scope.
  • Closures: Functions can remember the environment they were created in.
  • Higher-order functions: Functions that take other functions as arguments or return them.

This summary provides a brief overview of non-primitive data types in JavaScript, focusing particularly on arrays, objects, and functions, highlighting their definitions, characteristics, creation methods, and common functionalities.

Arrays

• Ordered collections of values containing multiple items.
• Dynamic size - can change in size
• Can hold different data types (numbers, strings, objects, etc.)
• Created using array literals let arr = [1, 2, 3]; or the Array constructor let arr = new Array(1, 2, 3);
• Common methods:
  • push(): Adds an item to the end.
  • pop(): Removes the last item.
  • shift(): Removes the first item.
  • unshift(): Adds an item to the front.
  • slice(): Returns a portion of the array.
  • map(): Creates a new array based on the results of a function.
  • filter(): Creates a new array with elements that pass a test.

Objects

• Collections of key-value pairs, where keys are strings and values can be any data type.
• Created using object literals let obj = {key1: value1, key2: value2}; or the Object constructor let obj = new Object();
• Can store functions as values (methods)
• Properties can be accessed using dot notation obj.key1 or bracket notation obj['key1']
• Common methods:
  • Object.keys(): Returns an array of keys.
  • Object.values(): Returns an array of values.
  • Object.entries(): Returns an array of [key, value] pairs.
  • Object.assign(): Copies values from one or more source objects to a target object.

Functions

• First-class objects that can be assigned to variables, passed as arguments, or returned from other functions.
• Created using function declaration function myFunction() { } or function expression let myFunction = function() { }; or Arrow functions let myFunction = () => { };
• Can return a value using the return statement.
• Can have parameters and arguments.
• Can be called repeatedly.
• Can be used as a method within objects.
• Common concepts:
  • Scope: Functions create their own scope.
  • Closures: Functions can remember the environment they were created in.
  • Higher-order functions: Functions that take other functions as arguments or return them.