Undefined check in JavaScript
27606
Detecting an undefined object property
10298
Difference between == and === in JavaScript
64111
Is my JavaScript validating enough?
64589
unchecked or unsafe operation error
119201
Why am I getting undefined is not a function when using jquery?
37350
checking each required input for empty value with jQuery
48991
How does this JavaScript/jQuery syntax work: (function( window, undefined ) { })(window)?
33682
how do I compare 2 functions in javascript
45322
jQuery Ajax results in undefined
113018
Javascript shorthand if
83782
How to check a not-defined variable in JavaScript
132062
Reference undefined
113905
How can I check whether a variable is defined in JavaScript?
152538
What is causing undefined control sequence?
45164
Do 'if' statements in JavaScript require curly braces?
79114
Is color undefined
22473
nested checkbox behavior check/uncheck