How can I check for "undefined" in JavaScript?
27606
Detecting an undefined object property
115191
Does Javascript have something like Ruby's method_missing feature?
119201
Why am I getting undefined is not a function when using jquery?
27136
Reference: What is variable scope, which variables are accessible from where and what are "undefined variable" errors?
90509
Does JavaScript have "Short-circuit" evaluation?
22042
How can I check whether a radio button is selected with JavaScript?
128669
How to check whether multiple values exist within an Javascript array
73021
Javascript : is given function empty?
114378
How to check if the string is empty?
84421
variable === undefined vs. typeof variable === "undefined"
72505
Automatically highlight undefined references
76406
Show reference label when it is undefined
113905
How can I check whether a variable is defined in JavaScript?
144673
Why does this JavaScript code print "undefined" on the console?
5451
How do I check if an element is hidden in jQuery?
44858
JavaScript isset() equivalent
53586
How can I type-check variables in Python?