let c1 = 'A'
let isLetter = /[a-z]/i.test(c1)
let isNumber = c1 >= '0' && c1 <= '9'
//isLetter is true
//isNumber is false
let c2 = '$'
let symbolList = "@#$%^&*"
let isInList = symbolList.includes(c2)
//isInList is true
console.log(`isLetter is ${isLetter}`)
console.log(`isNumber is ${isNumber}`)
console.log(`isInList is ${isInList}`)