Add curry

lib/util/curry.js

@@ -0,0 +1,30 @@
+/* eslint no-shadow:0 */
+export function curry1(fn) {
+  return function curried(a, b, c) {
+    const n = arguments.length;
+
+    if (n >= 1) return fn(a, b, c);
+    return curried;
+  };
+}
+
+export function curry2(fn) {
+  return function curried(a, b, c, d) {
+    const n = arguments.length;
+
+    if (n >= 2) return fn(a, b, c, d);
+    if (n === 1) return curry1((b, c, d) => fn(a, b, c, d));
+    return curried;
+  };
+}
+
+export function curry3(fn) {
+  return function curried(a, b, c, d, e) {
+    const n = arguments.length;
+
+    if (n >= 3) return fn(a, b, c, d, e);
+    if (n === 2) return curry1((c, d, e) => fn(a, b, c, d, e));
+    if (n === 1) return curry2((b, c, d, e) => fn(a, b, c, d, e));
+    return curried;
+  };
+}

test/util/curry-spec.js

@@ -0,0 +1,43 @@
+import { expect } from 'chai';
+import { curry1, curry2, curry3 } from '../../lib/util/curry';
+
+describe('curry1', () => {
+  it('can curry one arguments', () => {
+    const addOne = curry1((x) => x + 1);
+    expect(addOne(3)).to.equal(4);
+    expect(addOne()(3)).to.equal(4);
+  });
+
+  it('will take up to two extra arguments', () => {
+    const curried = curry1((a, b, c) => [a, b, c]);
+    expect(curried(1, 2, 3, 4)).to.eql([1, 2, 3]);
+  });
+});
+
+describe('curry2', () => {
+  it('can curry two arguments', () => {
+    const add = curry2((x, y) => x + y);
+    expect(add(3)(4)).to.equal(7);
+    expect(add()(3)()(4)).to.equal(7);
+    expect(add(3, 4)).to.equal(7);
+  });
+
+  it('will take up to two extra arguments', () => {
+    const curried = curry2((a, b, c, d) => [a, b, c, d]);
+    expect(curried(1, 2, 3, 4, 5)).to.eql([1, 2, 3, 4]);
+  });
+});
+
+describe('curry3', () => {
+  it('can curry three arguments', () => {
+    const add = curry3((x, y, z) => x + y + z);
+    expect(add(3)(4)(5)).to.equal(12);
+    expect(add()(3)()(4, 5)).to.equal(12);
+    expect(add(3, 4, 5)).to.equal(12);
+  });
+
+  it('will take up to two extra arguments', () => {
+    const curried = curry3((a, b, c, d, e) => [a, b, c, d, e]);
+    expect(curried(1, 2, 3, 4, 5, 6)).to.eql([1, 2, 3, 4, 5]);
+  });
+});