Using Globals

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Summary: How and why to use global variables within your trading strategy.

About

Using globals in this context is not so related to BacktestJS but more to regular Javascript usage. Never the less it is used quite a bit in strategies and will be explained in more detail below.

The reason why globals are used a lot is because anything within the function itself will reset every candle as it gets run inside a for loop.

For example if you make a variable called counter and do something like below, counter will always be 0 or 1 but never 2.

				
					import { BTH } from "../infra/interfaces"

export async function buyThreeTimes(bth: BTH) {
    // Define counter and add 1 to it
    let counter = 0
    counter++

    // This will always be 1 as the counter 
    // var gets reset to 0 every candle iteration
    console.log(counter)
}

In the example below we can see more of a use case in which you might use a global.

Example

				
					// Define imports
import { BTH } from "../infra/interfaces"

// DEFINE A GLOBAL HERE (ABOVE THE FUNCTION)
let higherThanLastCandleCount = 0

// Buy 3 times strategy
export async function buyThreeTimes(bth: BTH) {

    // Get last 2 candle closes
    const candles = bth.getCandles('close', 0, 2)

    // Buy if this close is more than last close
    if (candles[0] > candles[1]) {
        // Buy with 30% of total first time
        if (higherThanLastCandleCount === 0) await bth.buy({ amount: '30%' })

        // Buy with 20% of total second time
        else if (higherThanLastCandleCount === 1) await bth.buy({ amount: bth.orderBook.preBoughtQuoteAmount * .2 })

        // Buy with 10% of total first time
        else if (higherThanLastCandleCount === 2) await bth.buy({ amount: bth.orderBook.preBoughtQuoteAmount * .1 })

        // Increase higherThanLastCandleCount
        higherThanLastCandleCount++
    }

    // Sell if current candle is less than last candle
    else {
        await bth.sell()
        // Reset higher than last candle count
        higherThanLastCandleCount = 0
    }
}

In this example we buy if the current candle is more than the last candle. But we don’t buy with all of our money, we buy with 30% of our total the first time, then 20% if it happens next candle and lastly 10% of total if it happens for a third time. If the current candle is less than last candle then all gets sold and we reset the higher than last candle count to 0. Heres more of a breakdown

Total amount = $1000

if current candle is more than last candle buy with $300
If current candle is again higher than last candle buy with $200
If current candle is again higher than last candle buy with $100
If current candle is again higher than last candle don’t do anything (You only invest up to 60% of total)
If current candle is lower than last candle sell and reset amountOfTimesBought to 0
Lets say you sold and are now worth $2000
if current candle is more than last candle buy with $600
If current candle is again higher than last candle buy with $400
If current candle is lower than last candle sell and reset higherThanLastCandleCount to 0 (You only invested 50% of the total this time)
etc… the cycle continues

With BacktestJS you can

Using Globals

About

Example

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