Created
September 13, 2016 21:16
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An example of reducing a set of data
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/* | |
Implement a function that given two arbitrary dates ‘dateFrom’ and ‘dateTo’, will display a sorted list of the stocks based on their performance over those dates. For example: | |
*/ | |
const stocks = { | |
AAPL: [ | |
{ | |
'date': '2016-03-02', | |
'price': 98.32, | |
'dayChange': -1.5 | |
}, | |
{ | |
'date': '2016-03-03', | |
'price': 100.00, | |
'dayChange': 2.60 | |
}, | |
{ | |
'date': '2016-03-04', | |
'price': 101.2, | |
'dayChange': -1.22 | |
}, | |
{ | |
'date': '2016-03-07', | |
'price': 104.64, | |
'dayChange': 3.44 | |
} | |
], | |
FB: [ | |
{ | |
'date': '2016-03-02', | |
'price': 98.32, | |
'dayChange': -1.1 | |
}, | |
{ | |
'date': '2016-03-03', | |
'price': 100.00, | |
'dayChange': 1.68 | |
}, | |
{ | |
'date': '2016-03-04', | |
'price': 101.2, | |
'dayChange': 1.2 | |
}, | |
{ | |
'date': '2016-03-07', | |
'price': 104.64, | |
'dayChange': 3.44 | |
} | |
], | |
GOOGL: [ | |
{ | |
'date': '2016-03-02', | |
'price': 98.32, | |
'dayChange': -1.1 | |
}, | |
{ | |
'date': '2016-03-03', | |
'price': 100.00, | |
'dayChange': 1.68 | |
}, | |
{ | |
'date': '2016-03-04', | |
'price': 101.2, | |
'dayChange': -12 | |
}, | |
{ | |
'date': '2016-03-07', | |
'price': 104.64, | |
'dayChange': 1.44 | |
} | |
] | |
}; | |
const _ = require('underscore'); | |
const showPerformanceBetweenDates2 = (startDate, endDate) => { | |
const start = new Date(startDate).getTime(); | |
const end = new Date(endDate).getTime(); | |
const now = new Date().getTime() | |
if (start > end) { return console.log('Dates are out of order'); } | |
if (now - start > 31536000000) { return console.log('Start date is over 1 year old'); } | |
_.mapObject(stocks, (value, key) => { | |
stocks[key] = value.filter((s) => { | |
const thisDate = new Date(s.date).getTime(); | |
return thisDate >= start && thisDate <= end; | |
}) | |
.reduce((totalValue, currentDay) => (totalValue + currentDay.dayChange), 0); | |
}); | |
console.log(stocks); | |
}; | |
showPerformanceBetweenDates2('2016-03-03', '2016-03-04') |
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