We are frequently using the following code pattern in our JavaScript code if (typeof(some_variable) != 'undefined' && some_variable != null) { // Do something with some_variable } Is there...
How do I check a variable if it’s null or undefined and what is the difference between the null and undefined? What is the difference between == and ===...
I have a global variable in JavaScript (actually a window property, but I don’t think it matters) which was already populated by a previous script, but I don’t want...
Why is null considered an object in JavaScript? Is checking if ( object == null ) Do something the same as if ( !object ) Do something ? And...
I wanted to check whether the variable is defined or not. For example, the following throws a not-defined error alert( x ); How can I catch this error? 15...
I want to know what the difference is between null and undefined in JavaScript. 3 36
Which method of checking if a variable has been initialized is better/correct? (Assuming the variable could hold anything (string, int, object, function, etc.)) if (elem) { // or !elem...
How do I determine if variable is undefined or null? My code is as follows: var EmpName = $("div#esd-names div#name").attr('class'); if(EmpName == 'undefined'){ // DO SOMETHING }; <div id="esd-names">...
Is there a universal JavaScript function that checks that a variable has a value and ensures that it’s not undefined or null? I’ve got this code, but I’m not...
This question already has answers here: Detecting an undefined object property (50 answers) How to check a not-defined variable in JavaScript (15 answers) How to handle ‘undefined’ in JavaScript...