How to check if last character of a string is a digit/number by the fastest way in plain JavaScript?

Question

How to check if last character of a string is a digit/number in plain JavaScript?

function endsWithNumber(str){
  return str.endsWith(); // HOW TO CHECK IF STRING ENDS WITH DIGIT/NUMBER ???
}

var str_1 = 'Pocahontas';
var str_2 = 'R2D2';

if (endsWithNumber(str_1)) {
  console.log(str_1 + 'ends with a number');
} else {
  console.log(str_1 + 'does NOT end with a number');
}

if (endsWithNumber(str_2)) {
  console.log(str_2 + 'ends with a number');
} else {
  console.log(str_2 + 'does NOT end with a number');
}

Also I would like to know what would be the most fastest way? I guess it may sound ridiculous :D but in my usecase I will need this method very often so I think it could make a difference.

Answer 1

You can use Conditional (ternary) operator with isNaN() and String.prototype.slice():

function endsWithNumber(str){
  str = str.trim();
  if (!str) return 'Invalid input'; //return if input is empty
  return isNaN(str.slice(-1)) ? 'does NOT end with a number' : 'ends with a number';
}

console.log(endsWithNumber('Pocahontas'));
console.log(endsWithNumber('R2D2'));
console.log(endsWithNumber(''));