JavaScript offers eight basic data types:
To easily remember them, learn the mnemonic: NUNBBOSS, which stands for Null, Undefined, Number, Boolean, BigInt, Object, String, Symbol.
Now that we know there are eight data types, let's explore what these data types are used for:
| /* | |
| NULL: | |
| - Used to represent "nothing", "value unknown" or "empty". | |
| - We use null intentionally for missing values. | |
| - Null is not used to reference a "non existing object" | |
| */ | |
| let address = null; | |
| /* | |
| UNDEFINED: | |
| - The meaning of undefined is "value is not assigned". | |
| - We use undefined intentionally for missing values. | |
| */ | |
| let age; | |
| /* | |
| Number: | |
| - Represent both integer(whole numbers) and floating point numbers (decimals). | |
| - Used for math calculations. | |
| - There are some special numeric values: Infinity, -Infinity, NaN (Not a Number). | |
| */ | |
| let weight = 150; | |
| weight = 150.55; | |
| /* | |
| Boolean: | |
| - Has two possible values: true or false | |
| - used for logical operations | |
| */ | |
| let isChecked = true; | |
| var isVerified = false; | |
| /* | |
| BigInt: | |
| - Number cannot represent values larger than 2^53 - 1 or smaller than -2^53 - 1. | |
| - BigInt allow us to use really large numbers without limitations. | |
| - We create a BigInt by appending 'n' to the end of an integer. | |
| */ | |
| const bigNumber = 987654321987654321987654321n; | |
| /* | |
| Object: | |
| - Objects are used to store collections of data by using keys and values. | |
| */ | |
| let user = { | |
| name: "John", | |
| age: 31, | |
| occupation: "Software Developer", | |
| }; | |
| /* | |
| String: | |
| - Used for text and represented by quotes | |
| - Strings can be represented by "", '', `` | |
| */ | |
| let name = "Chris"; | |
| /* | |
| Symbol: | |
| - Used for unique identifiers | |
| - Often used to add unique property keys to an object | |
| */ | |
| const symbol = Symbol("foo"); |
Of the eight data types, seven are primitive. The term “primitive” means that a data type can contain only a single value. All primitive types are immutable, and we cannot set properties on them.
Objects are the only non-primitive type because they are used to store collections of data and more complex entities.
You might be thinking, “Hey, but I heard that everything in JavaScript is an object! If a string is not an object, how come I can do the following:
| "hi".toUpperCase(); // HI |
This logic makes the string “hi” appear as if it were an object because we are using a method on it. This is an illusion! JavaScript creates a temporary object when we want to use a method for a primitive type and then immediately discards it!