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
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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....
Alternatively, it can also be used as typeof() method in JavaScript.Syntax:typeof(variable); Example 1:str = "This is my place."; if (typeof str == String) { console.log('The variable is a String.'); } else { console.log('The variable is not a String.'); } ...
However, be cautious when using this method; if myVar had not been declared, the code would throw an error. Therefore, it’s typically safer to use the typeof method in scenarios where the variable might not be declared. Method 3: Using the void Operator The void operator is another ...
It get assigned to a variable when it is declared but not assigned any value. How to check if a variable is undefined?There are more than one way to check if a variable is undefined or not. Let's see them one by one. Using typeof operator Using strict equality operator Using void ...
Detect if BitLocker Protection Status is 0, enable Detect if variable has been previously declared? Detect integrated (onboard) GPU using WMI Detect mapped drive path and disconnect if exists determine 32 or 64bit OS? Determine if service exists? Dialog box - execute a command if no button is...
Check session if doesn't exists redirect to login page Check username and password is incorrect in asp.net check/Uncheck All checkboxlist items on click of checkbox checkbox and requiredfieldvalidator Checkbox Array?? checkbox checkchange using javascript Checkbox Checked Value is Always True Checkbox...
sumcurrentValiiargumentslengthisumargumentsicurrentValsumcurrentValexpect(addAny(9,9)).toEqual(jasmine.any(String));});}); Following is the output of the above code. Print Page Previous Next Advertisements
However, note that it is more efficient to use specific events, like, that only get dispatched when the element gets clicked. I wrotea bookin which I share everything I know about how to become a better, more efficient programmer.