JavaScript function similar to Python range()

Question

Is there a function in JavaScript similar to Python\'s range()?

I think there should be a better way than to write the following lines every time:

Answer 1

Is there a function in JavaScript similar to Python's range()?

As answered before: no, there's not. But you can make your own. I believe this is an interesting approach for ES6. It works very similar to Python 2.7 range(), but it's much more dynamic.

function range(start, stop, step = 1) 
{
    // This will make the function behave as range(stop)
    if(arguments.length === 1)
    {
        return [...Array(arguments[0]).keys()]
    }

    // Adjusts step to go towards the stop value
    if((start > stop && !(step < 0)) ||
       (start < stop && !(step > 0)))
    {
        step *= -1
    }

    let returnArray = []
    // Checks if i is in the interval between start and stop no matter if stop
    // is lower than start or vice-versa
    for(let i = start; (i-start)*(i-stop) <= 0; i += step)
    {
        returnArray.push(i)
    }
    return returnArray
}

This function can behave in three different ways (just like Python's range()):

1. range(stop)
2. range(start, stop)
3. range(start, stop, step)

These examples:

console.log(range(5))
console.log(range(-2, 2))
console.log(range(2, -2))
console.log(range(10, 20, 2))

Will give you the following output:

[ 0, 1, 2, 3, 4 ]
[ -2, -1, 0, 1, 2 ]
[ 2, 1, 0, -1, -2 ]
[ 10, 12, 14, 16, 18, 20 ]

Note that instead of iterating over the array with the in operator (like python), you have to use of. Thus the i variable assumes the value, and not the index, of the array's element.

for(let i of range(5))
{
    // do something with i...
}