JavaScript の reduce と reduceRight の練習

reduce_and_reduceRight.js

var a = [1, 2, 3];
function f(x, y) {
    return 2 * x + y;
}

var b = a.reduce(f, 4);
var c = a.reduceRight(f, 4);

// 43
console.log(b);
console.log(f(f(f(4, 1), 2), 3));
console.log(2 * (2 * (2 * 4 + 1) + 2) + 3);

// 49
console.log(c);
console.log(f(f(f(4, 3), 2), 1));
console.log(2 * (2 * (2 * 4 + 3) + 2) + 1);