How to check data type in javascript

• Numbers
• Strings
• Booleans
• Arrays Objects

Understanding Data Types in JavaScript is very important because it determines what values you can assign.

JavaScript has dynamic data types that mean the same variable can be used to hold different data types 

example 

var a;               // Datatype of a is undefined
a = 101;            // Datatype of a is a Number
a = "Qandeel";     // Datatype of a is a String

You can try the JavaScript typeof operator to check the data type of a variable

Example

console.log(typeof "text"); // text
console.log(typeof 5);     // number
console.log(typeof ][);   // object