Similarities in syntax, Di erences in meaning: Python vs. JavaScript helps in understanding the two programming languages. Learn more about it here.
It sometimes happens that two languages put different meanings on the same or similar syntax expression. When the both languages are of interest for a programmer, clarifying these bifurcation points helps to better understand the both languages in their basics and subtleties.
in with lists
2 in [2, 3]
In Python this evaluates to True, but in JavaScript to false. This is because in Python in checks if a value is contained in a list, so 2 is in [2, 3] as its first element. In JavaScript in is used with objects and checks if an object contains the property with the name expressed by the value. So JavaScript considers [2, 3] as an object or a key-value map like this:
{'0': 2, '1': 3}
and checks if it has a property or a key ‘2’ in it. Integer 2 is silently converted to string ‘2’.