Javascript - Combining multi-dimensional array with index

Question

I have an multidimensional array which looks like this:

[  
  ["1","2","3","4"],
  ["1","2","3","4"],
  ["1","2","3","4"], 
  ["1","2","3","4"]  
]

What I am hoping to accomplish is combining everything into a single array by adding the values of the array by its index.

Expected result:

[4,8,12,16] //(adding the 4 array values with appropriate index)

I see Lodash has a method _.zip, but that does not accept array of arrays as input to give the correct value. Is there an easy to accomplish this?

xdazz · Accepted Answer · 2016-02-23 01:45:19Z

3

If _.zip does not accept array of arrays as input, there is a technical to achieve it. _.zip.apply(null, array).

It could be done like below. (Note your bottom level elements are strings, so there is one more step to convert them to number.)

var data =[  
  ["1","2","3","4"],
  ["1","2","3","4"],
  ["1","2","3","4"], 
  ["1","2","3","4"]  
];

var result = _.map(_.zip.apply(null, data), function (n) {
  return _.sum(_.map(n, function(x) { return +x; }));
}); 

console.log(result);

The demo.

answered Feb 23, 2016 at 1:45

xdazz

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Comments

jwde · Accepted Answer · 2016-02-23 01:34:07Z

2

I'm interpreting your question as follows: map each element in the array to it's length plus the value of the previous element. Here is one way you could do that.

x = [  
  ["1","2","3","4"],
  ["1","2","3","4"],
  ["1","2","3","4"], 
  ["1","2","3","4"]  
]  
result = x.map(function(a) {
    return a.length;
}
for (i = 1; i < result.length; ++i) {
    result[i] += result[i - 1];
}

answered Feb 23, 2016 at 1:34

jwde

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