Check returned value by res is null
49
What is a NullPointerException, and how do I fix it?
94839
Check whether a string is not null and not empty
5377
Is there a standard function to check for null, undefined, or blank variables in JavaScript?
67597
Can constructor return a null object?
601
How do I test for an empty JavaScript object?
17732
Will code in a Finally statement fire if I return a value in a Try block?
128709
Why is there a `null` value in JavaScript?
93804
How to check for a Null value in VB.NET
97235
Test if any columns are NULL
35900
Lightning response.getReturnValue() question
40229
How do I check if a variable exists?
29684
How to check if an object is nullable?
158391
Most efficient way to check for DBNull and then assign to a variable?
90115
How can I list the nodes for which a Boolean value is FALSE or NULL?
49446
How to check for an undefined or null variable in JavaScript?
39781
Why does the is operator return false when given null?
114378
How to check if the string is empty?