Modern JavaScript and Python have a lot in common - for example the iteration protocol, generators, module import syntax, and async/await syntax should feel pretty similar. JS does not have comprehension syntax (e.g. the list, dictionary, set, and generator comprehensions available in Python). It is much more common to use functional programming patterns. Arrow functions in JS are analogous to lambdas in python. JS functions do not have keyword arguments. Instead, it is fairly common for functions to accept an "options" object as their final positional parameter, containing key-value pairs. JS does not differentiate between "items" and "attributes". They are all just properties on an object, accessed with either square brackets obj['propertyName'] or dot notation obj.propertyName. A JS object literal is kind of similar to a dictionary in python, but JS also now has Map and Set classes. JS has a contextual this keyword, instead of a conventionally-named self parameter for object methods. Methods are not auto-bound to objects like they are in python. The this keyword is provided to a method at call-time - for example if you call someObj.someMethod() or someObj['someMethod']() the dot notation and square bracket notation implicitly provides someObj as the value of this inside someMethod. However in the following code: let method = someObj.someMethod; method(); The this keyword will not be someObj - it will either be the global object or undefined depending on if you are using strict mode. Function objects also have call, apply, and bind methods which can be used to explicitly set the value of this. JS does not have magic methods like python has - so you can't override the behavior of builtin operators like you can in python. For example the === operator always compares values by strict equality (same type and value for primitives, referential equality for objects). JS classes do not support multiple inheritance, though multiple inheritance is possible via object prototypes. JS has a for...in loop as well as a for...of loop. The for...of loop is the one that works like for...in in python, which is easy to mix up. JS has both a null primitive and an undefined primitive, as opposed to Python's singular None. Obviously there are syntax differences - python uses a much more minimalist, significant-whitespace syntax, while JS has a more C-like syntax with more brackets, parens, semicolons, etc. And of course there are various other differences, but these are the ones that I think are most likely to trip you up when learning JS coming from a Python background. Answer from Deleted User on reddit.com