problem1a.js

const fs = require('fs');
const data = fs.readFileSync('input1.txt', 'utf8').split('\n').filter(e => e.length).map(s => parseInt(s));
console.log(data);
for (let i = 0; (i < data.length); i++) { 
  for (let j = i + 1; (j < data.length); j++) { 
    if (data[i] + data[j] === 2020) {
      console.log(data[i] * data[j]);
    }
  }
}