Task2a

.gitignore

@@ -1 +1,2 @@
 node_modules
+.git

returnsCalc.js

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+(function() {
+    'use strict';
+
+    var fs = require('fs');
+
+    function getTimeSeries(jsonObj, fieldName) {
+        var columnId = jsonObj.dataset.column_names.indexOf(fieldName);
+        return jsonObj.dataset.data.map(function(d) {
+            return {
+                date: new Date(d[0]),
+                value: d[columnId]
+            };
+        }).reverse();
+    }
+
+    function getStartDate(date) {
+        var result = new Date(date);
+        result.setDate(date.getDate() - 7);
+        return result;
+    }
+
+    function addStartAndReturn(d, i, data) {
+        d.start = getStartDate(d.date);
+
+        while (i >= 0 && data[i].date > d.start) {
+            i--;
+        }
+
+        if (i >= 0) {
+            d.startIndex = i;
+            d.startValue = data[i].value;
+            d.return = d.value / d.startValue - 1;
+        }
+
+        return d;
+    }
+
+    function getMinAndMax(returnSeries) {
+        return returnSeries.reduce(function(p, v) {
+            if (p == null) {
+                return {min: v, max: v};
+            }
+            return {
+                min: v.return < p.min.return ? v : p.min,
+                max: v.return > p.max.return ? v : p.max
+            };
+        }, null);
+    }
+
+    // Public API
+    module.exports = function(jsonObj, fieldName) {
+        var timeSeries = getTimeSeries(jsonObj, fieldName);
+
+        var returnSeries = timeSeries
+            .map(addStartAndReturn)
+            .filter(function(d) { return d.return; });
+
+        return getMinAndMax(returnSeries);
+    };
+
+    module.exports.getTimeSeries = getTimeSeries;
+    module.exports.getStartDate = getStartDate;
+    module.exports.addStartAndReturn = addStartAndReturn;
+    module.exports.getMinAndMax = getMinAndMax;
+}());

returnsCmd.js

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+var returnsCalc = require('./returnsCalc');
+var fs = require('fs');
+
+fs.readFile('./AAPL.json', 'utf8', function(err, data) {
+    if (err) {
+        return console.log(err);
+    }
+
+    var jsonObj = JSON.parse(data);
+    var minMax = returnsCalc(jsonObj, 'Adj. Close');
+    console.log(minMax);
+});

spec/getMinAndMaxSpec.js

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+/* global describe */
+describe('getMinAndMax', function() {
+    var returnsCalc = require('../returnsCalc');
+
+    it('is a function', function() {
+        var typeName = typeof(returnsCalc.getMinAndMax);
+        expect(typeName).toEqual('function');
+    });
+
+    it('Min and max should be both 2', function() {
+        var arr = [{return: 2}];
+        var result = returnsCalc.getMinAndMax(arr);
+        expect(result.min === 2);
+        expect(result.max === 2);
+    });
+
+    it('Min and max should be both 2 - multiple same', function() {
+        var arr = [{return: 2}, {return: 2}, {return: 2}];
+        var result = returnsCalc.getMinAndMax(arr);
+        expect(result.min === 2);
+        expect(result.max === 2);
+    });
+
+    it('Min and max should work with extreme values', function() {
+        var arr = [{return: Number.POSITIVE_INFINITY}, {return: 8}, {return: Number.NEGATIVE_INFINITY}];
+        var result = returnsCalc.getMinAndMax(arr);
+        expect(result.min === Number.NEGATIVE_INFINITY);
+        expect(result.max === Number.POSITIVE_INFINITY);
+    });
+
+    it('Min and max should work with fractions', function() {
+        var arr = [{return: 0.002}, {return: 0.0000002}, {return: 0.2}];
+        var result = returnsCalc.getMinAndMax(arr);
+        expect(result.min === 0.0000002);
+        expect(result.max === 0.2);
+    });
+
+});

spec/getStartDateSpec.js

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+/* global describe */
+describe('getStartDate', function() {
+    var returnsCalc = require('../returnsCalc');
+
+    it('is a function', function() {
+        var typeName = typeof(returnsCalc.getStartDate);
+        expect(typeName).toEqual('function');
+    });
+
+    it('should return a day 7 days earlier', function() {
+        var date = new Date('2015-10-20');
+        var result = returnsCalc.getStartDate(date);
+        expect(result.toISOString().substr(0, 10)).toEqual('2015-10-13');
+    })
+
+    it('should return a day 7 days earlier in previous year', function() {
+        var date = new Date('2015-01-01');
+        var result = returnsCalc.getStartDate(date);
+        expect(result.toISOString().substr(0, 10)).toEqual('2014-12-25');
+    })
+});

spec/getTimeSeriesSpec.js

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+/* global describe */
+describe('getTimeSeries', function() {
+    var returnsCalc = require('../returnsCalc');
+
+    it('is a function', function() {
+        var typeName = typeof(returnsCalc.getTimeSeries);
+        expect(typeName).toEqual('function');
+    });
+});