How to determine the data type of a JavaScript variable

Please tell me how to determine the data type of a variable in JavaScript.

typeofUse operators 
to determine the data type of a variable . 
You can also 
isInteger isNaN isArraymake judgments tailored to your needs by using etc.

How to determine data type using typeof operator

typeofThe operator returns a string indicating what data type the variable is.

typeof variable;

The usage is as follows.

let variable = 'hello';
console.log(typeof variable);  // 'string'

typeofOperators can determine data types such as:

• string: string type
• number: Numeric type
• boolean: Boolean type
• function: Functional type
• object: object type
• undefined: undefined type

Determining data type with “isInteger”, “isNaN”, and “isArray”

isInteger(value): Method to determine whether it is an integer .
Returns true if it is an integer, false otherwise.

isNaN(value): A global function that determines whether it is a number .
Returns false if it is a number, true otherwise.

Array.isArray(value): Method to determine whether it is an array .
Returns true if it is an array, false otherwise.

How to use each is as follows.

console.log(Number.isInteger(10));  // true
console.log(Number.isInteger(10.5));  // false

console.log(isNaN(10));  // false
console.log(isNaN('hello'));  // true

console.log(Array.isArray([1, 2, 3]));  // true
console.log(Array.isArray({}));  // false

Summary of “How to determine the data type of a variable”

” How to determine the data type of a variable ” is summarized below.

By accurately determining the data type, you can avoid program errors, so be sure to use it with this in mind.

The typeof operator seems easy to use. 
Also, isInteger, isNaN, and isArray seem useful.

In particular, isNaN is useful because you can use it like isNaN(parseInt()) to determine whether a string becomes NaN when converting it to a number.