We have arrays:
[1, 2, 3, 0]
[1, 2, 3]
[1, 2]
Need to get a one array, indexes which is will be like a sum of columns. Expected result:
[3, 6, 6, 0]
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Sometimes you get lucky and people don't even question the fact that you showed no efforts whatsoever. You got lucky ;)a-d– a-d2016-03-30 10:08:45 +00:00Commented Mar 30, 2016 at 10:08
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4 Answers
You can use Array.prototype.reduce() in combination with Array.prototype.forEach().
var array = [
[1, 2, 3, 0],
[1, 2, 3],
[1, 2]
],
result = array.reduce(function (r, a) {
a.forEach(function (b, i) {
r[i] = (r[i] || 0) + b;
});
return r;
}, []);
document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');8 Comments
Rayon
How does it happen ?
Nina Scholz
it iterates over the outer array and then adds each value of the inner array to the same position in the result array.
a-d
@NinaScholz reduce, my favorite!
Samurai Jack
I don't figure out what should I change to make this for rows instead of columns. Probably
table.reduce(function (r, a) { r.forEach(function(b, i) { a[i] = (a[i] || 0) + b; }); return a; }, []); is not the right way.Nina Scholz
@user3654571 it's not the right place to ask in comments another problem, but you could map the sums with
result = array.map(function (aa) { return aa.reduce(function (a, b) { return a + b; }); }); |
Basic for loop,
var arr = [[1, 2, 3, 0],[1, 2, 3],[1, 2]];
var res = [];
for(var i=0;i<arr.length;i++){
for(var j=0;j<arr[i].length;j++){
res[j] = (res[j] || 0) + arr[i][j];
}
}
console.log(res); //[3, 6, 6, 0]
answered Mar 30, 2016 at 10:03
Rajaprabhu Aravindasamy
67.2k17 gold badges107 silver badges133 bronze badges
Comments
function arrayColumnsSum(array) {
return array.reduce((a, b)=> // replaces two elements in array by sum of them
a.map((x, i)=> // for every `a` element returns...
x + // its value and...
(b[i] || 0) // corresponding element of `b`,
// if exists; otherwise 0
)
)
}
console.log(arrayColumnsSum([
[1, 2, 3, 0]
,[1, 2, 3]
,[1, 2]
]))
answered Mar 30, 2016 at 11:04
Michał Perłakowski
93.4k30 gold badges165 silver badges189 bronze badges
1 Comment
agravat.in
awsome, Thnks :)
You can do something like this using map() and reduce()
// function to get sum of two array where array length of a is greater than b
function sum(a, b) {
return a.map((v, i) => v + (b[i] || 0))
}
var res = [
[1, 2, 3, 0],
[1, 2, 3],
[1, 2]
// iterate over array to reduce summed array
].reduce((a, b) => a.length > b.length ? sum(a, b) : sum(b, a))
document.write('<pre>' + JSON.stringify(res, null, 3) + '</pre>');