CODEWITHSUNDEEP
arraysnode.js
irom
irom

Reputation: 3606

array comprehension in Nodejs v4.2.4

I have Python function returning me ip addresses of i.e. 10.1-2.128-256.1 (2nd byte changing from 1-2 and 3rd byte changing from 128 to 256)

def list1s():   
return ["10." + str(x) + "." + str(y) + ".1" for x in range(1, 3) for y in range(128, 256)]

I am trying to do the same in Nodejs v4.2.4. So far I found how to do range in NodeJS. I think next step would be to use map ?

function list1s(){    
    return Array.from(Array(256).keys()).slice(128,256)
}

Upvotes: 0

Views: 49

Answers (1)

Petr
Petr

Reputation: 6279

First, you need to wrap your range into a function:

functions range(begin, end) {
  return Array.from(Array(end).keys()).slice(begin, end);
}

After then, to get all possible combinations of x and y, you need to get a cartesian product of two arrays:

function cartesian() {
    var r = [], args = Array.from(arguments);
    args.reduceRight(function(cont, factor, i) {
        return function(arr) {
            for (var j=0, l=factor.length; j<l; j++) {
                var a = arr.slice(); // clone arr
                a[i] = factor[j];
                cont(a);
            }
        };
    }, Array.prototype.push.bind(r))(new Array(args.length));
    return r;
}

This function from two arrays [1,2] and [1,2] will produce an array [[1,1], [1,2], [2,1], [2,2]].

With these two helper functions making a list you need is easy:

function list() {
    return cartesian(range(1,3), range(128, 256)).map(function(args) {
       return '10.' + args[0] + '.' + args[1] + '.1';
    });
}

Upvotes: 1

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