Reference
Function and method references for JavaScript, Python.
Array.prototype.at
Read by index, including NEGATIVE ones — arr[-1] does not work, arr.at(-1) does.
Array.prototype.concat
Join arrays into a NEW one — array arguments are spread, other values appended.
Array.prototype.copyWithin
Shuffle a block of elements to another position in the same array — length never changes.
Array.prototype.every
Do ALL elements pass? An empty array answers TRUE — vacuous truth.
Array.prototype.fill
Overwrite a range with one value IN PLACE — and every slot gets the SAME reference.
Array.prototype.filter
Build a NEW array of the elements that pass a test — the length can shrink.
Array.prototype.find
The first element that passes a test, or undefined — not an array.
Array.prototype.findIndex
Position of the first element that passes a test, or -1.
Array.prototype.findLast
find and findIndex, searching from the END instead of the start.
ArithmeticError
Base class of ZeroDivisionError, OverflowError and FloatingPointError — catch it to handle any numeric failure at once.
AssertionError
Raised when an assert statement finds its condition false. Meant for catching bugs — python -O removes asserts entirely.
AttributeError
Raised when an attribute reference or assignment fails — obj.x where obj has no x.
BaseException
The root of every Python exception: defines args, str(), tracebacks, chaining and notes for all of them.
BufferError
Raised when a buffer operation cannot be performed — typically resizing a bytearray, BytesIO or array while a memoryview of it is still alive.
ConnectionError
Base class for connection failures: broken pipes, aborted, refused and reset connections.
DeprecationWarning
Warning category for features that are deprecated — aimed at developers, so it is hidden by default unless triggered directly by code in __main__.
EOFError
Raised when input() hits end-of-file before reading anything — and by pickle/marshal when the data runs out.
Exception
The base class of every ordinary error — the one to subclass for your own exceptions and the one to catch in catch-all handlers.