Check if a variable is a string using JavaScript

In this article, we will check if a variable is a string using JavaScript. We can check the variable by using many methods.

Below are the following methods through which we can check the type of variable is a string:

Approach 1: Using typeOf Operator

In this approach, we are using typeOf operator which tells us the type of the given value. we are getting the type of the value by the use of the typeOf operator and we are using if-else for returning our ans.

Example: This example shows the implementation of the above-explained approach.

Javascript

let boolValue = true;
let numValue = 17;
let bool, num;

if (typeof boolValue == "string") {
    bool = "is a string";
} else {
    bool = "is not a string";
}
if (typeof numValue == "string") {
    num = "is a string";
} else {
    num = "is not a string";
}
console.log(bool);
console.log(num);

Output

is not a string
is not a string

Approach 2: Using Instanceof Operator

The instanceof operator in JavaScript is used to check the type of an object at run time.

Syntax:

let gfg = objectName instanceof objectType

Example: This example shows the implementation of above-explained appraoch.

Javascript

let variable = new String();

if (variable instanceof String) {
  console.log("variable is a string.");
} else {
  console.log("variable is not a string.");
}

Output

variable is a string.

Approach 3: Underscore.js _.isString()

The _.isString() function is used to check whether the given object element is string or not.

Syntax:

_.isString( object );

Example: This example shows the implementation of above-explained appraoch.

Javascript

let _ = required("underscore");
let info = {
    Company: 'GeeksforGeeks',
    Address: 'Noida',
    Contact: '+91 9876543210'
};
console.log(_.isString(info));

let str = 'GeeksforGeeks';
console.log(_.isString(str));

Output:

false
true

Approach 4: Using Lodash _.isString() Method

In this approach, we are using the Lodah _.isString() method that returns boolean response for the given value.

Example: This example shows the implementation of above-explained appraoch.

Javascript

// Requiring the lodash library
const _ = require("lodash");

// Use of _.isString() method
console.log(_.isString('GeeksforGeeks'));
console.log(_.isString(true));

Output:

true
false