How can I determine if a JavaScript variable is defined in a page?
80608
JavaScript check if variable exists (is defined/initialized)
9417
Are there constants in JavaScript?
44858
JavaScript isset() equivalent
115620
Get variable name. javascript "reflection"
44112
"Variable" variables in Javascript?
15233
Event handler scope in Javascript
40229
How do I check if a variable exists?
117923
How to use JavaScript variables in jQuery selectors?
122591
How best to determine if an argument is not sent to the JavaScript function
120258
Check if element is visible in DOM
119228
Use a content script to access the page context variables and functions
131554
jQuery determining if element exists on page
137660
Avoid running the script if a variable is not defined
132096
How do you check if a JavaScript Object is a DOM Object?
85545
How to display JavaScript variables in a HTML page without document.write
105633
What characters are valid for JavaScript variable names?
22042
How can I check whether a radio button is selected with JavaScript?