Common Dupes

JS:

• How can I access and process nested objects, arrays or JSON?
• How to return the response from an asynchronous call
• Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference
• JavaScript closure inside loops – simple practical example

Python:

• List of lists changes reflected across sublists unexpectedly
• How do I clone a list so that it doesn't change unexpectedly after assignment?
• Strange result when removing item from a list while iterating over it
• How to remove items from a list while iterating?
• Why does "a == x or y or z" always evaluate to True?
• How to test multiple variables for equality against a single value?
• Importing installed package from script raises "AttributeError: module has no attribute" or "ImportError: cannot import name" (file named the same as imported module)
• Does Python have a string 'contains' substring method?
• TypeError: 'list' object is not callable in python (shadows builtin function, then tries to call builtin)
• How to use variables in SQL statement in Python?
• Access a particular field in arbitrarily nested JSON data