@nathanfaucett/array-reduce/src/index.js

applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value.

var isUndefined = require("@nathanfaucett/is_undefined");


module.exports = arrayReduce;


function arrayReduce(array, callback, initialValue) {
    var il = array.length - 1,
        value = initialValue,
        i;

    if (isUndefined(value)) {
        value = array[0];
        i = 0;
    } else {
        i = -1;
    }

    while (i++ < il) {
        value = callback(value, array[i], i, array);
    }

    return value;
}