Javascript: Multiply and Sum Two Arrays

Question

I have two arrays of equal length, and I need to multiply the corresponding (by index) values in each, and sum the results.

For example

var arr1 = [2,3,4,5];
var arr2 = [4,3,3,1];

would result in 34 (4*2+3*3+4*3+5*1).

What's the simplest to read way to write this?

Answer 1

var arr1 = [2,3,4,5];
var arr2 = [4,3,3,1];
console.log(arr1.reduce(function(r,a,i){return r+a*arr2[i]},0));
34

This shows the "functional" approach rather than the "imperative" approach for calculating the dot product of two vectors. Functional approach (which tends to be more concise) is preferred in such a simple function implementation as requested by the OP.