Data Types

JavaScript has several built-in data types that are used to represent different kinds of values. Understanding these data types is important when working with JavaScript code. Primitive Data Types: JavaScript has six primitive data types:

1. Number: Used to represent numeric values, including integers and floating-point numbers.

2. String: Used to represent text values.

3. Boolean: Used to represent true/false values.

4. Undefined: Used to represent a variable that has not been assigned a value.

5. Null: Used to represent a variable that has been explicitly set to a null value.

6. Symbol: Used to represent a unique identifier. Complex Data Types: JavaScript also has two complex data types:

7. Object: Used to represent collections of key/value pairs.

8. Function: Used to represent a block of code that can be executed.

• String: A sequence of characters, such as "Hello World". Strings can be enclosed in either single or double quotes.

• Number: Numeric values, including integers and floating-point numbers. For example, 10 and 3.14.

• Boolean: Represents a true/false value. The values true and false are the only possible values for a Boolean.

• Null: Represents a non-existent value. The value null represents a deliberate non-value.

• Undefined: Represents a value that has not been assigned. The value undefined represents a value that has not been assigned or a declared variable that has not been assigned a value.

• Object: A collection of properties and methods. Objects can be created using object literals or with the Object constructor.

• Array: An ordered list of values. Arrays are objects and can contain elements of any data type.

• Symbol :A unique and immutable data type that can be used as an identifier for object properties.

• The typeof operator in JavaScript is used to determine the data type of a value. It returns a string that represents the data type of the operand. The syntax for using typeof is:

  typeof operand;

  For example:

  let name = 'John Doe';
  console.log(typeof name); // "string"
   
  let age = 30;
  console.log(typeof age); // "number"
   
  let isMarried = true;
  console.log(typeof isMarried); // "boolean"
   
  let car = null;
  console.log(typeof car); // "object"
   
  let job;
  console.log(typeof job); // "undefined"

• It's important to note that in JavaScript, typeof null returns "object". This is considered a bug in the language and is a well-known issue.

• The typeof operator can be useful for debugging and for checking the data type of a value before performing operations on it. It can also be used to determine if a variable has been declared and assigned a value, by checking if the result of typeof is "undefined".

  1. Video: "Different Data Types in JavaScript | JavaScript Tutorial | Learn JavaScript" https://www.youtube.com/watch?v=O9by2KcR2v4 (opens in a new tab)

  2. Article: "JavaScript Weekly: Data Types and Mutability" https://medium.com/launch-school/javascript-weekly-data-types-and-mutability-e41ab37f2f95 (opens in a new tab)