Price alert snippet for monitoring market cap on assets exchanges.

price-alert-util.ts

/**
 * Price alert snippet
 * For monitoring market cap on assets exchanges
 * Precious Akin
 */

// Available exchange assets
enum ASSET {
    'NGN' = '\u20A6', // ₦
    'USD' = '$'
}

/**
 * Calculate percent change in value
 * @param oldPrice Initial value
 * @param newPrice Most recent value
 * @returns The percentage change between old and new value.
 */
const calcPercentDiff = (oldPrice:number, newPrice:number):number => {
    let diff = newPrice - oldPrice;
    let calcPrice = (diff)/oldPrice * 100;
    return Number(calcPrice.toFixed(2));
}

/**
 * People friendly money value
 * @param value An amount to format
 * @returns A comma-seperated value
 */
const formatMoney = (value:number):string => {
    return `${value.toString().replace(/(\d)(?=(\d{3})+(?!\d))/g, '$1,')}`;
};

/**
 * Check price change in the network 
 * @param oldData The previous market data
 * @param newData The most recent market data
 */
export const priceCheck = (oldData, newData) => {
    const diff = calcPercentDiff(oldData, newData);
    let msg;
    oldData = ASSET.NGN + formatMoney(oldData);
    newData = ASSET.NGN + formatMoney(newData);
    if(oldData==newData) {
        msg = (`${ASSET.NGN + newData}`);
        return {diff, msg, xValue:'GAIN'};
    }
    if(oldData < newData) {
        msg = (`Price has increased -> From ${oldData} to ${newData}`);
        return {diff, msg, xValue:'GAIN'};
    }
    if(oldData > newData) {
        msg = (`Price has decreased -> From ${oldData} to ${newData}`);
        return {diff, msg, xValue:'LOSS'};
    }
}

// Use case
const {msg, diff, xValue} = priceCheck(39000, 80000);
console.log(`${msg}
${Math.abs(diff)}% (${xValue})`);

Note: This is a Typescript file; to run with node you must have Typescript installed globally and then transpile to javascript file.
Run the below commands if you have Node.js installed on your machine.

• npm install -g typescript
• tsc price-alert-util.ts && node price-alert-util.js