number to text

function numberToWords (n) {
    const num = ["zero", "one", "two", "three","four","five","six", "seven", "eight", "nine"]
    const first = ["ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "seventeen", "eighteen", "nineteen",]
    const second = ["", "", "twenty", "thirty", "fourty", "fifty", "sixty", "seventy", "eighty", "ninety"]
    let output = []
    const sNumber = n.toString()
    const len = sNumber.length
    let str = ''
    for (var i = 0; i < len; i += 1) {
    	output.push(+sNumber.charAt(i));
    }
   	if (output[len - 1] !== undefined) {
    	// single digit
    	str += ' '+ num[output[len-1]]
    }
    if (output[len - 2] !== undefined) {
    	// two digit
      if(output[len - 2] == 1) {
      	str = ' '+ first[output[len - 1]] 
      } else {
      	str += ' '+ second[output[len-2]]
      }
    }
    if (output[len - 3] !== undefined) {
    	// three digit
    	str += ' and hundred'
      str += ' '+ num[output[len-3]]
    }
    if (output[len - 4] !== undefined) {
    	// four digit
    	str += ' thousand'
      str += ' '+ num[output[len-4]]
    }
    
    return str.split(" ").reverse().toString().replace(/,/g , " ")
}

console.log(numberToWords(9))