how to check for null or undefined in Javascript for an ID
4521
Is there an "exists" function for jQuery?
141197
In JavaScript, is there an easier way to check if a property of a property exists?
128709
Why is there a `null` value in JavaScript?
152510
Why is document.GetElementById returning null
37350
checking each required input for empty value with jQuery
125549
Does assigning null remove all event handlers from an object?
5451
How do I check if an element is hidden in jQuery?
76735
document.getElementById("someId") Vs. someId
29684
How to check if an object is nullable?
83354
Nullable types: better way to check for null or zero in c#
15097
Is there any difference between IS NULL and =NULL
144544
How to handle NULL values when inserting with the Dataloader(.io)
38241
How do I check for nulls in an '==' operator overload without infinite recursion?
59266
How does jQuery work when there are multiple elements with the same ID value?
114378
How to check if the string is empty?
126341
Avoiding IF ELSE due to variable been NULL
703
What is the best way to test for an empty string with jquery-out-of-the-box?