Add commas to a number.
npm install commafy
var commafy = require('commafy')
console.log(commafy(1000000)) // '1,000,000'
console.log(commafy(1000)) // '1,000'
console.log(commafy(1000.123)) // '1,000.123'
console.log(commafy(100)) // '100'
console.log(commafy(1e4)) // '10,000'