let characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
let result = ''
let length = 10 // Customize the length here.
for (let i = length; i > 0; --i) result += characters[Math.round(Math.random() * (characters.length - 1))]
console.log(result)