Created
November 13, 2019 23:50
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| /* | |
| A classic stock trading pattern happens when a 9-Day Moving Average (9-DMA) crosses the 50-Day Moving Average (50-DMA). | |
| This can be indicative of a bullish or a bearish setup, depending on the direction. When the 9-DMA crosses below the 50-DMA | |
| from above, it is Bearish. When the 9-DMA cross above the 50-DMA from below, it is Bullish. | |
| Write a program that reads in a series of dates and prices, calculates the 9-DMA and 50-DMA, | |
| then returns the dates of any bullish signals that occurred. | |
| NOTE: The Moving Average cannot be calculated for a given day if there is not enough historical data to cover | |
| the period in question. For example, a series of prices that begin on January 1 cannot have a 9-DMA calculated | |
| before January 9 since 9 days of historical prices do not exist until January 9. Input: A series of Date|Price | |
| pairs in non-localized format. Dates will follow ISO 8601 format YYYY-MM-DD. Prices will be a two-decimal value | |
| with no currency indications. | |
| */ | |
| function checkBullish () { | |
| let prices = [] | |
| let dates = [] | |
| let bullish = "" | |
| for (let i = 0; i < input.length; i++){ | |
| dates.push(input[i].split("|").first) //capture only dates from input and push to [] | |
| prices.push(input[i].split("|").last) //capture only prices from input and push to [] | |
| } | |
| //set beginning and end limits for 9-DMA & 50-DMA | |
| let beginNineDma = 0 | |
| let endNineDma = 8 | |
| let beginFiftyDma = 0 | |
| let endFiftyDma = 49 | |
| while(endFiftyDma < prices.length - 1) { //while 50-DMA's limit is valid | |
| let subarray9 = prices.splice(beginNineDma, endNineDma) //target the 9-day period | |
| let sumNine = subarray9.reduce((previous, current) => current += previous) //sum to calculate avg | |
| let avgNine = sumNine/subarray9.length //9-Day Moving Average | |
| let subarray50 = prices.splice(beginFiftyDma, endFiftyDma) //target the 50-day period | |
| let sumFifty = subarray50.reduce((previous, current) => current += previous) //sum to calculate avg | |
| let avgFifty = sumFifty/subarray50.length //50-Day Moving Average | |
| if(avgNine > avgFifty){ //if bullish | |
| bullish = dates[endNineDma] //capture 9-DMA's last day | |
| return bullish | |
| } else { | |
| beginNineDma = endNineDma + 1 //increment beginning and end limits for 9-DMA | |
| endNineDma += 9 | |
| beginFiftyDma = endFiftyDma + 1 //increment beginning and end limits for 50-DMA | |
| endFiftyDma += 50 | |
| } | |
| } | |
| } | |
| if (bullish == "") { //bullish was not found | |
| return null | |
| } | |
| } |
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