However, the variable must already be declared. Below is the sample code: let b = undefined; console.log(b === undefined); // true This method will throw a ReferenceError if the variable is undeclared. Read More: Selenium with JavaScript : Getting Started with Automation Testing 3. Using...
Whether you are a beginner or an experienced developer, this guide will help you navigate the nuances of variable checks in JavaScript. Method 1: Using the typeof Operator One of the simplest ways to check if a variable is undefined is by using the typeof operator. This operator returns a...
Now to check whether a given variable is a string or not, we'll use a JavaScript operator called typeof.Syntax:typeof variable; This operator returns the data type of the variable specified after it. If the variable is of string data type, it will return a string....
Sometimes, you may need to validate the input values of a string variable and make sure that it is not empty or null. This can be useful for preventing errors, handling edge cases, or implementing conditional logic. In this tutorial, we will give you three examples of how to check if a...
To check if a variable is an array in Javascript is essential to handle data appropriately. We will discuss three different approaches to check if a variable is an array or not. We are having an array and a string, and our task is to check if a variable is an array in JavaScript. ...
Topic: JavaScript / jQueryPrev|NextAnswer: Use the typeof operatorIf you want to check whether a variable has been initialized or defined (i.e. test whether a variable has been declared and assigned a value) you can use the typeof operator....
JavaScript Define a Function to Check If a Variable is a String 6 7 8 9 // Defining a function 10 function isString(myVar) { 11 return (typeof myVar === 'string'); 12 } 13 14 // Sample variables 15 var x = 10; 16 var y = true; 17 var z = "...
JavaScript provides several ways to check if a variable is a string. One of the most common methods is to use thetypeofoperator, which returns the type of a variable. For example, the following code checks if a variable named “myVar” is a string: ...
To avoid the mistake of initializing a variable tonull, we can use like this: if (typeof variable === 'undefined' || variable === null) { // variable is undefined or null Solution 4: In JavaScript, a variable can be defined, but hold the valueundefined. ...
Javascript Boolean Type Introduction Using the typeof operator, we can check the datatype of a variable. If the variable is a Boolean value, typeof will return the string 'boolean'. Copy vara =Boolean(true);varb = false;//www.java2s.comvarc ="";vard = newDate();if(typeofa ==='...