The Quite Nice and Fairly Accurate Intro to JS Primitive Data Types (pt. 1)
JavaScript has two main categories of data types: primitives and objects. A primitive (or a primitive value or a primitive data type), as described in the JavaScript documentation, is the data that is not an object and has no methods. JavaScript is a dynamically typed language, meaning variables are not bound to any specific data type. Instead, the type is determined at runtime. There are 6 primitive data types in JavaScript: Boolean, Number, String, Null, Undefined, Symbol (introduced in ES6) From ES2020, there's also a 7th primitive data type: BigInt (for handling arbitrarily large integers) 1. Boolean Boolean is a logical data type which can only have two values: true or false; It is a YES-NO switch; Logical operation results in a boolean value; let isActive = true; console.log(typeof isActive); // "boolean" Common Use Cases Controlling the flow of an application Logical conditions in if statements 2. Number Number is a numeric data type in the double-precision 64-bit floating point format. In JS, number represents both integers and floating points. let intNum = 42; // Integer let floatNum = 3.14; // Floating-point number let expNum = 5e3; // Exponential notation (5000) let negativeNum = -10; // Negative number console.log(typeof intNum); // "number" Special Number Values Infinity (positive infinity) -Infinity (negative infinity) NaN (Not a Number, usually from invalid calculations) Common Use Cases Mathematical calculations Representing numeric data 3. String A string is a sequence of characters used to represent text. In JS, a string is inside of double or single quotes. ES6 also introduced template literals or template strings. let singleQuoteStr = 'Hello'; let doubleQuoteStr = "World"; let templateStr = `Hello, ${doubleQuoteStr}!`; console.log(typeof singleQuoteStr); // "string" Common Use Cases Storing and manipulating text data Dynamically constructing strings using template literals 4. Null null represents "nothing" or an intentional absence of value. It is often used to indicate that a variable should have no value. Note: The typeof null is 'object'. This is a known bug in JavaScript that has existed since its early days but was never fixed for backward compatibility.(why null is object) let emptyValue = null; console.log(typeof emptyValue); // "object" Common Use Cases Explicitly indicating the absence of a value 5. Undefined Undefined is a data type that it stands for a value that is not defined; let notAssigned; console.log(notAssigned); // undefined console.log(typeof notAssigned); // "undefined" Common use case: Check if a variable is assigned with a value 6. Symbol (ES6) Symbol is a unique and immutable primitive value introduced in ES6. It is commonly used as unique property keys. let sym1 = Symbol("id"); let sym2 = Symbol("id"); console.log(sym1 === sym2); // false (each Symbol is unique) console.log(typeof sym1); // "symbol" Common Use Cases Creating unique object keys to prevent naming conflicts Implementing privacy in objects 7. BigInt (ES2020) Introduced in ES2020, BigInt allows you to store very large integers beyond Number.MAX_SAFE_INTEGER. let bigNumber = 9007199254740991n; // The 'n' at the end makes it a BigInt console.log(typeof bigNumber); // "bigint" Common Use Cases Storing cryptographic keys Working with extremely large numbers References: A quick overview of JavaScript symbols JavaScript Documentation JavaScript Data Types Explained Primitives method's
JavaScript has two main categories of data types: primitives and objects.
A primitive (or a primitive value or a primitive data type), as described in the JavaScript documentation, is the data that is not an object and has no methods.
JavaScript is a dynamically typed language, meaning variables are not bound to any specific data type. Instead, the type is determined at runtime.
There are 6 primitive data types in JavaScript: Boolean, Number, String, Null, Undefined, Symbol (introduced in ES6)
From ES2020, there's also a 7th primitive data type:
BigInt (for handling arbitrarily large integers)
1. Boolean
Boolean is a logical data type which can only have two values: true or false; It is a YES-NO switch; Logical operation results in a boolean value;
let isActive = true;
console.log(typeof isActive); // "boolean"
Common Use Cases
- Controlling the flow of an application
- Logical conditions in if statements
2. Number
Number is a numeric data type in the double-precision 64-bit floating point format. In JS, number represents both integers and floating points.
let intNum = 42; // Integer
let floatNum = 3.14; // Floating-point number
let expNum = 5e3; // Exponential notation (5000)
let negativeNum = -10; // Negative number
console.log(typeof intNum); // "number"
Special Number Values
- Infinity (positive infinity)
- -Infinity (negative infinity)
- NaN (Not a Number, usually from invalid calculations)
Common Use Cases
- Mathematical calculations
- Representing numeric data
3. String
A string is a sequence of characters used to represent text. In JS, a string is inside of double or single quotes. ES6 also introduced template literals or template strings.
let singleQuoteStr = 'Hello';
let doubleQuoteStr = "World";
let templateStr = `Hello, ${doubleQuoteStr}!`;
console.log(typeof singleQuoteStr); // "string"
Common Use Cases
- Storing and manipulating text data
- Dynamically constructing strings using template literals
4. Null
null represents "nothing" or an intentional absence of value.
It is often used to indicate that a variable should have no value.
Note: The typeof null is 'object'. This is a known bug in JavaScript that has existed since its early days but was never fixed for backward compatibility.(why null is object)
let emptyValue = null;
console.log(typeof emptyValue); // "object"
Common Use Cases
- Explicitly indicating the absence of a value
5. Undefined
Undefined is a data type that it stands for a value that is not defined;
let notAssigned;
console.log(notAssigned); // undefined
console.log(typeof notAssigned); // "undefined"
Common use case:
- Check if a variable is assigned with a value
6. Symbol (ES6)
Symbol is a unique and immutable primitive value introduced in ES6.
It is commonly used as unique property keys.
let sym1 = Symbol("id");
let sym2 = Symbol("id");
console.log(sym1 === sym2); // false (each Symbol is unique)
console.log(typeof sym1); // "symbol"
Common Use Cases
- Creating unique object keys to prevent naming conflicts
- Implementing privacy in objects
7. BigInt (ES2020)
Introduced in ES2020, BigInt allows you to store very large integers beyond Number.MAX_SAFE_INTEGER.
let bigNumber = 9007199254740991n; // The 'n' at the end makes it a BigInt
console.log(typeof bigNumber); // "bigint"
Common Use Cases
- Storing cryptographic keys
- Working with extremely large numbers
References:
A quick overview of JavaScript symbols
