How i can substract and sum results all arrays in array

Question

I have a few arrays in array :

([[10,0],[3,5],[5,8]])

I try substract all inner arrays a - b and then sum results ( example : 10 - 0 = 10, 3-5 = -2, 5-8 = -3, 10+(-2)+(-3) = 5;

My try:

 var el;
 return array.reduce((a, b) => a - b );

But my result came out Nan, now Im understood, in my code i want substring array from array - bad idea. I know how do this with using for or something like that, my question is:

how i can do this with use reduce or other ''modern'' method?

Thanks for help.

PS sorry for my English skill ;)

Answer 1

You can use reduce() method like this.

 var data = [[10,0],[3,5],[5,8]] var result = data.reduce((r, e) => r + (e[0] - e[1]), 0); console.log(result) 

Answer 2

Flexible solution, the size of the nested arrays doesn't matter, it will still return a proper result.

 const count = (arr) => arr.reduce((s, v) => { s += v.reduce((a,b) => a - b); return s; }, 0); let arr1 = [ [10, 0], [3, 5], [5, 8] ], arr2 = [ [5, 4, 1], [3, 5, 5], [5, 8] ]; console.log(count(arr1)); console.log(count(arr2)); 

Answer 3

Something like this? You were close, but be sure to have an initial value of 0 and dereference the inner arrays into a and b like so:

 var array = [[10,0],[3,5],[5,8]]; var result = array.reduce((prev, [a, b]) => prev + (a - b), 0); console.log(result); 

Answer 4

const arr = ([[10,8],[3,5],[5,8]]);
arr.map(pair => pair[0] - pair[1]).reduce((a,b) => a + b)

Answer 5

You could reduce the outer and inner arrays.

 var array = [[10, 0], [3, 5], [5, 8]], result = array.reduce(function (r, a) { return r + a.reduce(function (x, y) { return x - y; }) }, 0); console.log(result);