clock

Author: Ryan

clock/README.md

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+# Clock
+
+Implement a clock that handles times without dates.
+
+Create a clock that is independent of date.
+
+You should be able to add and subtract minutes to it.
+
+Two clocks that represent the same time should be equal to each other.
+
+## Setup
+
+Go through the setup instructions for JavaScript to
+install the necessary dependencies:
+
+http://exercism.io/languages/javascript
+
+## Making the Test Suite Pass
+
+Execute the tests with:
+
+    jasmine-node .
+
+In many test suites all but the first test have been skipped.
+
+Once you get a test passing, you can unskip the next one by
+changing `xit` to `it`.
+
+## Source
+
+Pairing session with Erin Drummond [https://twitter.com/ebdrummond](https://twitter.com/ebdrummond)
+
+## Submitting Incomplete Problems
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
+

clock/clock.js

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+const pipe = (first, ...fns) => (...args) => fns.reduce((acc, fn) => fn(acc), first(...args))
+
+const pad = (x) => x < 10 ? `0${x}` : x
+const mod = (val) => (x) => x % val
+const abs = (val) => (x) => x < 0 ? val + x : x
+
+const hoursPlusMins = (hours, mins) => hours + Math.floor(mins / 60)
+
+const Clock = class {
+  constructor(hours, mins = 0) {
+    this.hours = hours
+    this.mins = mins
+  }
+
+  static at(...args) {
+    return new Clock(...args)
+  }
+
+  equals(clock) {
+    return this.toString() === clock.toString()
+  }
+
+  plus(mins) {
+    this.mins += mins
+    return this
+  }
+
+  minus(mins) {
+    this.mins -= mins
+    return this
+  }
+
+  toString() {
+    const hours = pipe(hoursPlusMins, mod(24), abs(24), pad)(this.hours, this.mins)
+    const mins = pipe(mod(60), abs(60), pad)(this.mins)
+    return `${hours}:${mins}`
+  }
+}
+
+module.exports = Clock

clock/clock.spec.js

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+var at = require('./clock').at;
+
+describe('Clock', function () {
+
+  describe('Creating a new clock with an initial time', function () {
+
+    it('on the hour', function () {
+      expect(at(8).toString()).toEqual('08:00');
+    });
+
+    it('past the hour', function () {
+      expect(at(11, 9).toString()).toEqual('11:09');
+    });
+
+    it('midnight is zero hours', function () {
+      expect(at(24, 0).toString()).toEqual('00:00');
+    });
+
+    it('hour rolls over', function () {
+      expect(at(25, 0).toString()).toEqual('01:00');
+    });
+
+    it('hour rolls over continuously', function () {
+      expect(at(100, 0).toString()).toEqual('04:00');
+    });
+
+    it('sixty minutes is next hour', function () {
+      expect(at(1, 60).toString()).toEqual('02:00');
+    });
+
+    it('minutes roll over', function () {
+      expect(at(0, 160).toString()).toEqual('02:40');
+    });
+
+    it('minutes roll over continuously', function () {
+      expect(at(0, 1723).toString()).toEqual('04:43');
+    });
+
+    it('hour and minutes roll over', function () {
+      expect(at(25, 160).toString()).toEqual('03:40');
+    });
+
+    it('hour and minutes roll over continuously', function () {
+      expect(at(201, 3001).toString()).toEqual('11:01');
+    });
+
+    it('hour and minutes roll over to exactly midnight', function () {
+      expect(at(72, 8640).toString()).toEqual('00:00');
+    });
+
+    it('negative hour', function () {
+      expect(at(-1, 15).toString()).toEqual('23:15');
+    });
+
+    it('negative hour rolls over', function () {
+      expect(at(-25, 0).toString()).toEqual('23:00');
+    });
+
+    it('negative hour rolls over continuously', function () {
+      expect(at(-91, 0).toString()).toEqual('05:00');
+    });
+
+    it('negative minutes', function () {
+      expect(at(1, -40).toString()).toEqual('00:20');
+    });
+
+    it('negative minutes rolls over', function () {
+      expect(at(1, -160).toString()).toEqual('22:20');
+    });
+
+    it('negative minutes rolls over continuously', function () {
+      expect(at(1, -4820).toString()).toEqual('16:40');
+    });
+
+    it('negative hour and minutes both roll over', function () {
+      expect(at(-25, -160).toString()).toEqual('20:20');
+    });
+
+    it('negative hour and minutes both roll over continuously', function () {
+      expect(at(-121, -5810).toString()).toEqual('22:10');
+    });
+
+    describe('Adding and subtracting minutes', function () {
+
+      it('add minutes', function () {
+        expect(at(10, 0).plus(3).toString()).toEqual('10:03');
+      });
+
+      it('add no minutes', function () {
+        expect(at(6, 41).plus(0).toString()).toEqual('06:41');
+      });
+
+      it('add to next hour', function () {
+        expect(at(0, 45).plus(40).toString()).toEqual('01:25');
+      });
+
+      it('add more than one hour', function () {
+        expect(at(10, 0).plus(61).toString()).toEqual('11:01');
+      });
+
+      it('add more than two hours with carry', function () {
+        expect(at(0, 45).plus(160).toString()).toEqual('03:25');
+      });
+
+      it('add across midnight', function () {
+        expect(at(23, 59).plus(2).toString()).toEqual('00:01');
+      });
+
+      it('add more than one day (1500 min = 25 hrs)', function () {
+        expect(at(5, 32).plus(1500).toString()).toEqual('06:32');
+      });
+
+      it('add more than two days', function () {
+        expect(at(1, 1).plus(3500).toString()).toEqual('11:21');
+      });
+
+      it('subtract minutes', function () {
+        expect(at(10, 3).minus(3).toString()).toEqual('10:00');
+      });
+
+      it('subtract to previous hour', function () {
+        expect(at(10, 3).minus(30).toString()).toEqual('09:33');
+      });
+
+      it('subtract more than an hour', function () {
+        expect(at(10, 3).minus(70).toString()).toEqual('08:53');
+      });
+
+      it('subtract across midnight', function () {
+        expect(at(0, 3).minus(4).toString()).toEqual('23:59');
+      });
+
+      it('subtract more than two hours', function () {
+        expect(at(0, 0).minus(160).toString()).toEqual('21:20');
+      });
+
+      it('subtract more than two hours with borrow', function () {
+        expect(at(6, 15).minus(160).toString()).toEqual('03:35');
+      });
+
+      it('subtract more than one day (1500 min = 25 hrs)', function () {
+        expect(at(5, 32).minus(1500).toString()).toEqual('04:32');
+      });
+
+      it('subtract more than two days', function () {
+        expect(at(2, 20).minus(3000).toString()).toEqual('00:20');
+      });
+
+    });
+
+    describe('Construct two separate clocks, set times, test if they are equal', function () {
+
+      it('clocks with same time', function () {
+        expect(at(15, 37).equals(at(15, 37))).toBeTruthy();
+      });
+
+      it('clocks a minute apart', function () {
+        expect(at(15, 36).equals(at(15, 37))).toBeFalsy();
+      });
+
+      it('clocks an hour apart', function () {
+        expect(at(14, 37).equals(at(15, 37))).toBeFalsy();
+      });
+
+      it('clocks with hour overflow', function () {
+        expect(at(10, 37).equals(at(34, 37))).toBeTruthy();
+      });
+
+      it('clocks with hour overflow by several days', function () {
+        expect(at(3, 11).equals(at(99, 11))).toBeTruthy();
+      });
+
+      it('clocks with negative hour', function () {
+        expect(at(22, 40).equals(at(-2, 40))).toBeTruthy();
+      });
+
+      it('clocks with negative hour that wraps', function () {
+        expect(at(17, 3).equals(at(-31, 3))).toBeTruthy();
+      });
+
+      it('clocks with negative hour that wraps multiple times', function () {
+        expect(at(13, 49).equals(at(-83, 49))).toBeTruthy();
+      });
+
+      it('clocks with minute overflow', function () {
+        expect(at(0, 1).equals(at(0, 1441))).toBeTruthy();
+      });
+
+      it('clocks with minute overflow by several days', function () {
+        expect(at(2, 2).equals(at(2, 4322))).toBeTruthy();
+      });
+
+      it('clocks with negative minute', function () {
+        expect(at(2, 40).equals(at(3, -20))).toBeTruthy();
+      });
+
+      it('clocks with negative minute that wraps', function () {
+        expect(at(4, 10).equals(at(5, -1490))).toBeTruthy();
+      });
+
+      it('clocks with negative minute that wraps multiple times', function () {
+        expect(at(6, 15).equals(at(6, -4305))).toBeTruthy();
+      });
+
+      it('clocks with negative hours and minutes', function () {
+        expect(at(7, 32).equals(at(-12, -268))).toBeTruthy();
+      });
+
+      it('clocks with negative hours and minutes that wrap', function () {
+        expect(at(18, 7).equals(at(-54, -11513))).toBeTruthy();
+      });
+
+    });
+
+  });
+
+});