Python list comprehensions nodejs/javascript [duplicate]

Question

Is there anything similar to pythons list comprehension for nodejs/javascript? If there is not then is it possible to make a function that has similar behavior for example

# Example 1

list_one = [[1, 2], [3, 4], [5, 6], [7, 8]]
someOfList = sum(x[1] for x in list_one)
print(someOfList) # prints 20

# Example 2
combined = "".join([str( ( int(x) + int(y) ) % 10) for x, y in zip("9999", "3333")])
print(combined) # prints 2222

Etc? Or would you have to make functions for each comprehension like behavior? I know you can make functions for each of those, but if you use a lot of list comprehensions code can get long

Answer 1

List comprehensions put into a language's syntax what would normally be done with map and filter.

So given a Python list comprehension, you can also use map and filter:

# Python - preferred way
squares_of_odds = [x * x for x in a if x % 2 == 1]

# Python - alternate way
map(lambda x: x * x, filter(lambda x: x % 2 == 1, a))

although comprehensions are preferred in Python. JavaScript has map and filter so you can use those now.

// JavaScript
a.map(function(x){return x*x}).filter(function(x){return x%2 == 1})

The upcoming version of JavaScript will have array comprehensions in the language:

[ x*x for (x of a) if (x % 2 === 1) ]

To see what is available now in the upcoming version, see this compatibility table. As of this writing, you can see they are available in Firefox.