Top "Undefined" questions

A variable is undefined if it has not been assigned a value.

JavaScript "cannot read property "bar" of undefined

I've got a function that takes 3 parameters. The problem I have is one of the parameters is a property of …

javascript undefined
JavaScript check if value is only undefined, null or false

Other than creating a function, is there a shorter way to check if a value is undefined,null or false …

javascript null undefined
Javascript array value is undefined ... how do I test for that

I am trying to test to see whether a Javascript variable is undefined. You will see that I am not …

javascript arrays undefined
php $_GET and undefined index

A new problem has arisen for me as I tried to run my script on a different PHP Server. ON …

php undefined
How to compare variables to undefined, if I don’t know whether they exist?

In JavaScript you can declare a variable and if it’s undefined, you can check variable == undefined; I know that, …

javascript undefined
Passing Variable through JavaScript from one html page to another page

I have two pages - "page 1" and "page 2". On page 1 there's an text-box with a value of e.g. 100 and …

javascript html variables undefined global
Count of "Defined" Array Elements

Given following array: var arr = [undefined, undefined, 2, 5, undefined, undefined]; I'd like to get the count of elements which are defined (…

javascript undefined
Checking for Undefined In React

I have a scenario where I'm passing data from a reducer into my react state. data: { "id": 1, "title": "Test", "content": { "…

reactjs components redux undefined
When is null or undefined used in JavaScript?

I am really confused as to when JavaScript returns null or undefined. Also different browsers seem to be returning these …

javascript null undefined
golang "undefined" function declared in another file?

I'm trying to write a basic go program that calls a function on a different file, but a part of …

go undefined func