How to check if last character of a string is a digitnumber by the fastest way in plain JavaScript? - Stack Overflow

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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');
}

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.

• javascript
• string
• ends-with

Share Improve this question Follow edited May 1, 2021 at 6:11 bensiu-acc 9288 bronze badges asked Dec 1, 2019 at 9:20 RE666RE666 9111 silver badge99 bronze badges 1

• @str, my bad totally forgot about "NaN". So then, var str = "R2D2"; -> isNaN(str[str.length - 1]) === false && typeof +str[str.lenght - 1] === "number; – Krusader Commented Dec 1, 2019 at 9:31

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 7

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(''));

function endsWithNumber( str: string ): boolean {

    return str && str.length > 0 && str.charAt( str.length - 1 ).match( /[0-9A-Za-z]/ );
}

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