JavaScript has 8 Datatypes: String, Number, Bigint, Boolean, Undefined, Null, Symbol, and Object.

// String:
let firstName = "Emily";
let lastName = "VonDuck";

// Number:
let length = 8;
let weight = 1.5;

// Bigint:
let x = BigInt("738905435368978785421");

// Boolean (true or false):
let x = 3;
let y = 4;
let z = 5;

(x < y)       // Returns true
(x > z)       // Returns false

// Undefined (the variable has no value yet):
let car;      // Value is undefined, type is undefined

// (or the variable has its value emptied):
car = undefined;

// Null (the variable has no value yet):
let car = null;      // Value is defined, type is null

// Null (using dot notation):
obj.propertyName = null;

// Null (using bracket notation):
obj["propertyName"] = null;

JavaScript works from left to right. And when trying to combine a number with a string will treat the number as a string.

In the following, it will first add the two numbers, and when it reaches the string will convert the number to a string in order to combine it with the string.

let x = 12 + 4 + "Maserati"; // 16Maserati

In the following, since the string comes first and the number 16 will then be combined with it, it will be converted to a string “Maserati16”. Then when combined with another number, that number will also need to be converted to a string first.

let x = "Maserati" + 12 + 4; // Maserati124

The typeof operator returns the type of a variable or expression.

typeof 7              // Returns "number"
typeof 3.14           // Returns "number"
typeof (5)            // Returns "number"
typeof (2 + 4)        // Returns "number"
typeof "4"            // Returns "string"

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