JavaScript Stock Profit Calculator

JavaScript Stock Profit Calculator

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Overview

A JavaScript library for calculating the gain / loss of stock market transactions.

I started trading last 2014 to learn more about investing. My colleague helped me by providing references and tools. One of the tools is a stock profit calculator made in MS Excel. I thought of creating a stock market application for Android before but did not have the time to finish it. Instead, I extracted the code of the stock calculator and created this project.

Feel free to raise any suggestion / concern. I hope this library can help others.

Features

• Simple API
• Dynamic Stockbroker Creation
• Customizable Transaction Fees
• Uses BigNumber of Math.js
• Transaction Fee Breakdown

Getting Started

1. Import the JavaScript files.

    <!--  Dependencies -->
    <script src="http://cdnjs.cloudflare.com/ajax/libs/mathjs/1.6.0/math.min.js"></script>
   
    <!-- Core library files -->
    <script src="broker.js"></script>
    <script src="stock.calculator.js"></script>
   
    <!-- [Optional] -->
    <script src="brokers/broker-col.js"></script>
   

   • Dependencies:
     • Math.js
   • Core library files:
     • broker.js - contains the Broker class.
     • stock.calculator.js - contains the StockCalculator class.
   • Optional files:
     • broker-col.js - contains the Broker implementation for COLFinancial named as ColBroker.
     • Note: As of the moment, this is the only pre-created broker available.

2. Create a custom / use a pre-created stockbroker.

    var broker1 = new Broker("Broker Name"); // Create a new broker instance
    var broker2 = window.ColBroker; // Or use the default instance
   

3. Add transaction fees to broker instance.

    broker.addFee({
      name: 'commission',
      descrip: 'Commission',
      handler: function() { 
        return 'max(0.0025 * grossTradeAmt, 20)'; 
      }
    }, FeeType.BUY, FeeType.SELL);
   

   • Broker#addFee( feeObj, feeType... ) function accepts at least two parameters.
     • Fee
       • name - The variable name of the transaction fee that can be used by other fee handlers during evaluation.
       • descrip - The description of the transaction fee.
       • handler - A function that returns a String to be evaluated by Math.js.
     • Fee Type(s)
       • BUY
       • SELL
     • Note: grossTradeAmt is the default available variable for fee handlers.

4. Create an instance of the calculator.

    var calc = new StockCalculator( broker );
   

5. Compute gain / loss.

    calc.compute( 8000, 1.35, 1.40);
   

   • StockCalculator#compute(noOfShares, buyPrice, sellPrice [, showDetails]) function requires three parameters.
     • noOfShares - The total number of shares involved in the transaction.
     • buyPrice - The price of the stock bought.
     • sellPrice - The price of the stock sold.
     • showDetails - [Optional] - A boolean flag that indicates whether transaction fee breakdown will be included or not. Default is false.

6. Check the results.

    { 
      "gain" : 279.1,
      "gainPercent" : 2.5766581178117147,
      "actualBuy" : 1.3539825,
      "actualSell" : 1.38887
    }
   

   For the detailed result, click here to view it. (Extracted it to a separate link due to its verbosity.)