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A JavaScript variable can hold 8 types of data:
// String let color = "Yellow";
let lastName = "Johnson";
// Number let length = 16;
let weight = 7.5;
// BigInt let x = 1234567890123456789012345n;
let y = BigInt(1234567890123456789012345)
// Boolean let x = true;
let y = false;
// Object const person = {firstName:"John", lastName:"Doe"};
// Array object const cars = ["Saab", "Volvo", "BMW"];
// Date object const date = new Date("2022-03-25");
// Undefined let x;
let y;
// Null let x = null;
let y = null;
// Symbol const x = Symbol();
const y = Symbol();You can use the JavaScript typeof operator to find the type of a JavaScript variable. The typeof operator returns the type of a variable or an expression:
Example typeof "" // Returns "string" typeof "John" // Returns "string" typeof "John Doe" // Returns "string"
Example typeof 0 // Returns "number" typeof 314 // Returns "number" typeof 3.14 // Returns "number" typeof (3) // Returns "number"
Formula
typeof (3 + 4) // Returns"number"
A string (a text string) is a series of characters like "John Doe". Strings are written with quotes. You can use single or double quotes:
// Using double quotes:
let carName1 = "Volvo XC60";// Using single quotes:
let carName2 = 'Volvo XC60';Try it Yourself » You can use quotes inside a string, as long as they don't match the quotes surrounding the string:
// Single quote inside double quotes:
let answer1 = "It's alright";// Single quotes inside double quotes:
let answer2 = "He is called 'Johnny'";// Double quotes inside single quotes:
let answer3 = 'He is called "Johnny"';Try it Yourself »