lodash/test/curry.js

import assert from 'assert';
import lodashStable from 'lodash';
import { slice, stubArray } from './utils.js';
import curry from '../curry.js';
import placeholder from '../placeholder.js';
import bind from '../bind.js';
import partial from '../partial.js';
import partialRight from '../partialRight.js';

describe('curry', function() {
  function fn(a, b, c, d) {
    return slice.call(arguments);
  }

  it('should curry based on the number of arguments given', function() {
    var curried = curry(fn),
        expected = [1, 2, 3, 4];

    assert.deepStrictEqual(curried(1)(2)(3)(4), expected);
    assert.deepStrictEqual(curried(1, 2)(3, 4), expected);
    assert.deepStrictEqual(curried(1, 2, 3, 4), expected);
  });

  it('should allow specifying `arity`', function() {
    var curried = curry(fn, 3),
        expected = [1, 2, 3];

    assert.deepStrictEqual(curried(1)(2, 3), expected);
    assert.deepStrictEqual(curried(1, 2)(3), expected);
    assert.deepStrictEqual(curried(1, 2, 3), expected);
  });

  it('should coerce `arity` to an integer', function() {
    var values = ['0', 0.6, 'xyz'],
        expected = lodashStable.map(values, stubArray);

    var actual = lodashStable.map(values, function(arity) {
      return curry(fn, arity)();
    });

    assert.deepStrictEqual(actual, expected);
    assert.deepStrictEqual(curry(fn, '2')(1)(2), [1, 2]);
  });

  it('should support placeholders', function() {
    var curried = curry(fn),
        ph = curried.placeholder;

    assert.deepStrictEqual(curried(1)(ph, 3)(ph, 4)(2), [1, 2, 3, 4]);
    assert.deepStrictEqual(curried(ph, 2)(1)(ph, 4)(3), [1, 2, 3, 4]);
    assert.deepStrictEqual(curried(ph, ph, 3)(ph, 2)(ph, 4)(1), [1, 2, 3, 4]);
    assert.deepStrictEqual(curried(ph, ph, ph, 4)(ph, ph, 3)(ph, 2)(1), [1, 2, 3, 4]);
  });

  it('should persist placeholders', function() {
    var curried = curry(fn),
        ph = curried.placeholder,
        actual = curried(ph, ph, ph, 'd')('a')(ph)('b')('c');

    assert.deepStrictEqual(actual, ['a', 'b', 'c', 'd']);
  });

  it('should use `_.placeholder` when set', function() {
    var curried = curry(fn),
        _ph = placeholder = {},
        ph = curried.placeholder;

    assert.deepEqual(curried(1)(_ph, 3)(ph, 4), [1, ph, 3, 4]);
    delete placeholder;
  });

  it('should provide additional arguments after reaching the target arity', function() {
    var curried = curry(fn, 3);
    assert.deepStrictEqual(curried(1)(2, 3, 4), [1, 2, 3, 4]);
    assert.deepStrictEqual(curried(1, 2)(3, 4, 5), [1, 2, 3, 4, 5]);
    assert.deepStrictEqual(curried(1, 2, 3, 4, 5, 6), [1, 2, 3, 4, 5, 6]);
  });

  it('should create a function with a `length` of `0`', function() {
    lodashStable.times(2, function(index) {
      var curried = index ? curry(fn, 4) : curry(fn);
      assert.strictEqual(curried.length, 0);
      assert.strictEqual(curried(1).length, 0);
      assert.strictEqual(curried(1, 2).length, 0);
    });
  });

  it('should ensure `new curried` is an instance of `func`', function() {
    function Foo(value) {
      return value && object;
    }

    var curried = curry(Foo),
        object = {};

    assert.ok(new curried(false) instanceof Foo);
    assert.strictEqual(new curried(true), object);
  });

  it('should use `this` binding of function', function() {
    var fn = function(a, b, c) {
      var value = this || {};
      return [value[a], value[b], value[c]];
    };

    var object = { 'a': 1, 'b': 2, 'c': 3 },
        expected = [1, 2, 3];

    assert.deepStrictEqual(curry(bind(fn, object), 3)('a')('b')('c'), expected);
    assert.deepStrictEqual(curry(bind(fn, object), 3)('a', 'b')('c'), expected);
    assert.deepStrictEqual(curry(bind(fn, object), 3)('a', 'b', 'c'), expected);

    assert.deepStrictEqual(bind(curry(fn), object)('a')('b')('c'), Array(3));
    assert.deepStrictEqual(bind(curry(fn), object)('a', 'b')('c'), Array(3));
    assert.deepStrictEqual(bind(curry(fn), object)('a', 'b', 'c'), expected);

    object.curried = curry(fn);
    assert.deepStrictEqual(object.curried('a')('b')('c'), Array(3));
    assert.deepStrictEqual(object.curried('a', 'b')('c'), Array(3));
    assert.deepStrictEqual(object.curried('a', 'b', 'c'), expected);
  });

  it('should work with partialed methods', function() {
    var curried = curry(fn),
        expected = [1, 2, 3, 4];

    var a = partial(curried, 1),
        b = bind(a, null, 2),
        c = partialRight(b, 4),
        d = partialRight(b(3), 4);

    assert.deepStrictEqual(c(3), expected);
    assert.deepStrictEqual(d(), expected);
  });
});