javascript - Currying a function that takes infinite arguments

Question

Using ES5, how do you curry a function that takes infinite arguments.

function add(a, b, c) {
    return a + b + c;
}

The function above takes only three arguments but we want our curried version to be able to take infinite arguments.

Hence, of all the following test cases should pass:

var test = add(1);

test(2);     //should return 3
test(2,3);   //should return 6
test(4,5,6); //should return 16

Here is the solution that I came up with:

function add(a, b, c) {
    var args = Array.prototype.slice.call(arguments);

    return function () {
        var secondArgs = Array.prototype.slice.call(arguments);
        var totalArguments = secondArgs.concat(args);

        var sum = 0;

        for (i = 0; i < totalArguments.length; i++) {
            sum += totalArguments[0];
        }

        return sum;
    }
}

However, I have been told that it's not very “functional” in style.

Answer 1

Method 1: Using partial

A simple solution would be to use partial as follows:

Function.prototype.partial = function () {
    var args = Array.prototype.concat.apply([null], arguments);
    return Function.prototype.bind.apply(this, args);
};

var test = add.partial(1);

alert(test(2));     // 3
alert(test(2,3));   // 6
alert(test(4,5,6)); // 16

function add() {
    var sum = 0;
    var length = arguments.length;
    for (var i = 0; i < length; i++)
        sum += arguments[i];
    return sum;
}