@extra-array/accumulate/index.js

'use strict';
function accumulate(x, fr, acc) {
    var init = arguments.length <= 2;
    var a = [], i = -1;
    for (var v of x) {
        if (init) {
            acc = v;
            ++i;
            init = false;
        }
        else
            acc = fr(acc, v, ++i, x);
        a.push(acc);
    }
    return a;
}
module.exports = accumulate;