JavaScript Data Types & Data Structure

In JavaScript, data types specifies the kind of values stored in variables.

JavaScript has a dynamic typing system. It means that variables can hold values of any data type.

JavaScript is a weakly typed language. This means that variables do not have explicitly declared data types, and the interpreter determines the type of a value at runtime based on its usage.

There are two main categories of JavaScript data types: primitive and complex data types.

Understanding data types is crucial in programming. It is essential to be aware of the data types to write correct and efficient code.

Primitive Data Types:

Primitive data types are immutable which means their values cannot be changed once assigned.

• Number : This represents both integers and floating-point numbers.

  // Example of number let age = 18; let height = 1.76;
  

• BigInt : This represents large integers that are too large to be stored in the standard 'number' type.

  // Example of BigInt let largeNumber = 12345678901232345678904545454554n;
  

• String : This represents a sequence of characters (text). It is used to store textual data. Strings are written within single or double quotes.

  // Example of string data let message = "Hello World!";
  

• Boolean : This represents logical values: true or false.

  // Example of boolean data let isCorrect = true;
  

• Undefined : This represents a variable which is declared but no value is assigned to it.

  // Example of undefined data let firstName; console.log(typeof firstName) // undefined
  

• Null : This represents the absence of a value.

  // Example of null data type let noValue = null;
  

• Symbol :: This is a unique and immutable primitive data type used to create unique object keys.

  // Example of symbol data type let symId = Symbol('id');
  

Complex Data Types:

Complex data types are mutable which means their properties can be modified after creation.

• Object as Data Type : Object is a collection of key-value pairs, where keys are string data type and values can be of any data type.

  // Example of symbol data type let person = { name: "John", age: 18};
  

• Array as Data Type : Array is a special type of object that can store an ordered list of values.

  // Example of array let fruits = ["banana", "orange", "apple"];
  

• Function as Data Type : Functions are first-class objects. They can be assigned to variables, passed as arguments, or returned from other functions.

  // Example of function function addNumber(a, b) { return a + b; } let sum = addNumber(5, 7);
  

• Date as Data Type : A Date is an object that represents a specific point in time.

  // Example of Date let Now = new Date();
  

• Set as Data Type : A Set is a collection of unique values. Duplicate values are automatically discarded in set.

  // Example of Set let uniqueNumbers = new Set([1, 2, 3, 3, 5]);
  

• Map as Data Type : A Map is a collection of key-value pairs. In Map, keys can be of any data type.

  // Example of map let map = new Map(); map.set("name", "Jones");
  

In JavaScript, data structure is a way of organizing and storing data for efficient access and modification.

• Object as Data Structure : In JavaScript, an object is a collection of key-value pairs. Object's keys (properties) are strings or symbols, and the values can be any type. Object is a versatile and flexible data structure that allow to store and organize information in a flexible manner.

  // Example of object const student = { name: "John Smith", age: 18, courses: ["Math", "Chemistry", "Physics"], }; console.log(student.name); // gets value of name property console.log(student.courses[1]); // gets 2nd course name student.age = 20; // Modifies age console.log(student.age); //Output: 20 student.grade = 12; // Adds property to the object console.log(student.grade); //Output: 12
  

• Array as Data Structure : An array is a collection of elements. Each element has an index and the element can be accessed using its index. Array supports common methods like push(), pop(), shift(), and unshift().

  // Example of array let fruits = ["apple", "banana"]; fruits.push("orange"); // Adds orange to the end of array console.log(fruits); // Output: [ "apple", "banana", "orange" ] fruits.pop(); // removes the lase element console.log(fruits); // Output: [ "apple", "banana" ] fruits.unshift("cherry"); // Adds cherry to the beginning console.log(fruits); // Output: [ "cherry", "apple", "banana" ]
  

• Function as Data Structure : Functions can be used as objects. They can hold properties just like any other object.

  // Example of function function student(name, age) { student.info = { name: name, age: age }; } student("John", 18); console.log(student.info.name); //Output: John
  

• Date as Data Structure : A Date is an object that is used to represent and manipulate dates and times. The Date object provides many methods to perform different tasks with the year, month, day, etc. of a date.

  // Example of Date let currentDate = new Date(); //get current date time console.log(currentDate); console.log(currentDate.getFullYear()); // get year console.log(currentDate.getMonth()); //get month (0-11) console.log(currentDate.toDateString()); //get date
  

• Set as Data Structure : In JavaScript, a Set is a built-in data structure. A Set is a collection of unique values. Duplicate values are automatically discarded. Set has methods to manipulate elements of the set.

  // Example of Set let numSet = new Set([1, 2, 3, 3, 4]); // a set of numbers console.log(numSet); // Output { 1, 2, 3, 4 } (no duplicate element) numSet.add(5); // Adds 5 to the set console.log(numSet); // Output { 1, 2, 3, 4, 5 } numSet.delete(2); // Removes 2 from set console.log(numSet); // Output { 1, 3, 4, 5 } console.log(numSet.has(3)); // Output: true console.log(numSet.size); // Output: 4
  

• Map as Data Structure : In Javascript, a Map is another built-in data structure which is used to store a collection of key-value pairs. In Map, keys can be of any data type. Map's methods like set(), get(), has(), and delete() allow to manipulate the key-value pairs.

  // Example of map const studentMap = new Map(); studentMap.set('name', 'John'); // adds key-value pair studentMap.set('age', 10); // Add key-value pair console.log(studentMap); // Output: { "name" : "John", "age" : 10 } console.log(studentMap.get('age')); // Output: 10 studentMap.delete('age'); console.log(studentMap); // Output: { "name" : "John" }
  

Practice the above JavaScript code in the following JavaScript Editor. Try more JavaScript data types and data structure code in the following editor and click Execute button to check the output. The output will be displayed in JavaScript Code Output section.