JS - Data Types

JavaScript has 8 built-in data types (with the latest ECMAScript standard):

• We have the Primitives ones:

  • Null
  • Boolean
  • Undefined
  • Number
  • BigInt
  • String
  • Symbol

• and the Objects.

And you can check the type of each data type with the typeof operator:

let helloMessage = "Hello World";
typeof(helloMessage); //Output: "string"

let myAge = 32;
typeof(myAge); //Output: "number"

const myPerson = {
    name: 'Yves',
    age: 32,
}
typeof(myPerson); //Output: "object"

We have also have undefined and undeclared which is basically when you define a variable without a value (the default value is undefined). And undeclared is just that the value hasn’t been never declared.

Useful Resources:

• MDN JS Data Structures
• You Don’t Know JS Yet: Types & Grammar Second Edition (WIP)