JavaScript Function Currying Sample Code

I’ll introduce sample code for function currying written in JavaScript (ES5/ES6).

JavaScript Function Currying Sample Code

The key point is defining a value method on function resultFn and returning the function itself with return resultFn;.

Since functions are also objects, both function resultFn and var resultFn are objects, so you can define a result method on them with resultFn.result = function () {}.

Reference: 関数もオブジェクトである - JavaScriptの関数とメソッド：CodeZine（コードジン）

Function Currying ES5

function resultFn function example

function add(x) {
    var sum = x;

    function resultFn(y) {
        sum += y;
        return resultFn;
    }

    resultFn.result = function () {
        return sum;
    };
    return resultFn;
}

var resultFn = function (y) {} method example

function add(x) {
    var sum = x;

    var resultFn = function (y) {
        sum += y;
        return resultFn;
    };
    resultFn.result = function () {
        return sum;
    };

    return resultFn;
}

Function Currying ES6 (ES2015)

function resultFn function example

function add(x) {
    let sum = x;

    function resultFn(y) {
        sum += y;
        return resultFn;
    }

    resultFn.result = function () {
        return sum;
    };
    return resultFn;
}

const resultFn = (y) => {} method example

function add(x) {
    let sum = x;

    const resultFn = (y) => {
        sum += y;
        return resultFn;
    };
    resultFn.result = function () {
        return sum;
    };

    return resultFn;
}

Function Currying add method execution result

> add(2)(3)(4).result
[Function]
> add(2)(3)(4).result()
9

That’s all from the Gemba.