creating function within function – method “buy” is not defined

I get the error method “buy is not defined.”. What is wrong in the below code? Please can you let me know where I am going wrong?

var Portfolio = function() {

  let stockHoldings = new Map();
  
   function buy(trade) {
    let tradesForTicker = stockHoldings.get(trade.ticker);
    if(tradesForTicker == null){
      stockHoldings.set(trade.ticker,[trade]);
    }else{
      tradesForTicker.push(trade);
    }
  }

   function sell(trade) {
      let ticker = trade.ticker;  
      let tradesForTicker = stockHoldings.get(ticker);
      let precision = 5;
      if(tradesForTicker != null){
          let quantityToSell = Number(Number(trade.quantity).toFixed(precision));
          while(quantityToSell > 0) {
            quantityToSell = Number(Number(quantityToSell).toFixed(precision));          
            if(tradesForTicker.length > 0){
              let nextTradeToSell =  tradesForTicker[0];

              if(nextTradeToSell.quantity == quantityToSell){
                quantityToSell = 0;
                tradesForTicker.splice(0,1);
              } 
              else if (nextTradeToSell.quantity < quantityToSell){
                  quantityToSell = quantityToSell - nextTradeToSell.quantity;
                  tradesForTicker.splice(0,1);
              }else {
                nextTradeToSell.quantity = nextTradeToSell.quantity - quantityToSell;
                quantityToSell = 0;
              }
            }
          }
          if(tradesForTicker.length == 0){
            stockHoldings.delete(ticker)
          }
      }
  }

  this.stockHoldings = function() {
    return stockHoldings();
  }
};

function generetePortfolio(tickers, actions, quantities, prices){
  let portfolio = new Portfolio();
  for(var i=0;i< tickers.length; i++){
    let ticker = tickers[i].toString();
    let action = actions[i].toString();
    let quantity = quantities[i].toString();
    let price = prices[i].toString();

    let transactionTrade = new Trade(ticker,quantity,price,action);

    if(transactionTrade.isBuyOrDrip()){
        portfolio.buy(transactionTrade);
    }
    if(transactionTrade.isSell()){
      portfolio.sell(transactionTrade);
    }
  }
  return portfolio();
}

Further EDIT:

//Added method to generate total qty and avg price, BUT THIS DOES NOT WORK

function myPositions(tickers, actions, quantities, prices){
  let portfolio = generetePortfolio(tickers, actions, quantities, prices);  
  let returnArray = [];
  portfolio.stockHoldings.forEach((value, key) => {  
      let totalQuantity = 0;
      let avgPrice = 0;
      let totalCost = 0;
      value.map( trade => {
        totalQuantity += trade.quantity ;
        totalCost += trade.quantity * trade.price;
      });

      avgPrice = totalCost/totalQuantity;      
      returnArray.push([key, totalQuantity,avgPrice]);
  } )
  return returnArray;
}

Answer

You are trying to use properties of your portfolio object assuming that it will be an object based on Portfolio constructor but it is not.

A constructor function implicitly returns this. Now the only place you have used this inside the function is to attach one property stockHoldings to it.

You need to attach the other properties too.

What is happening under the hood can be thought of simply as : a local this empty object is created implicitly. It is returned in the end implicitly.

var Portfolio = function () {
 // this = {};  (implicitly)


  let stockHoldings = new Map();
  
   function buy(trade) {
    let tradesForTicker = stockHoldings.get(trade.ticker);
    if(tradesForTicker == null){
      stockHoldings.set(trade.ticker,[trade]);
    }else{
      tradesForTicker.push(trade);
    }
  }

   function sell(trade) {
      let ticker = trade.ticker;  
      let tradesForTicker = stockHoldings.get(ticker);
      let precision = 5;
      if(tradesForTicker != null){
          let quantityToSell = Number(Number(trade.quantity).toFixed(precision));
          while(quantityToSell > 0) {
            quantityToSell = Number(Number(quantityToSell).toFixed(precision));          
            if(tradesForTicker.length > 0){
              let nextTradeToSell =  tradesForTicker[0];

              if(nextTradeToSell.quantity == quantityToSell){
                quantityToSell = 0;
                tradesForTicker.splice(0,1);
              } 
              else if (nextTradeToSell.quantity < quantityToSell){
                  quantityToSell = quantityToSell - nextTradeToSell.quantity;
                  tradesForTicker.splice(0,1);
              }else {
                nextTradeToSell.quantity = nextTradeToSell.quantity - quantityToSell;
                quantityToSell = 0;
              }
            }
          }
          if(tradesForTicker.length == 0){
            stockHoldings.delete(ticker)
          }
      }
  }

  this.stockHoldings = stockHoldings;
  this.buy = buy;
this.sell = sell;

  // return this;  (implicitly)

};

function generetePortfolio(tickers, actions, quantities, prices){
  let portfolio = new Portfolio();
  for(var i=0;i< tickers.length; i++){
    let ticker = tickers[i].toString();
    let action = actions[i].toString();
    let quantity = quantities[i].toString();
    let price = prices[i].toString();

    let transactionTrade = new Trade(ticker,quantity,price,action);

    if(transactionTrade.isBuyOrDrip()){
        portfolio.buy(transactionTrade);
    }
    if(transactionTrade.isSell()){
      portfolio.sell(transactionTrade);
    }
  }
  return portfolio();
}

Also, the function for stockHoldings does not seem right. You should be returning the map right.