How to get only the numbers of a string in Javascript?

Question

I wonder if there are functions that return only the numeric values of a string, if there is not, what is the simplest and efficient way to implement?

Example:

apenasNumeros("5tr1ng");

Upshot:

51

Answer 1

function apenasNumeros(string) 
{
    var numsStr = string.replace(/[^0-9]/g,'');
    return parseInt(numsStr);
}

The simplest way:

1. Use regex to delete all non-number characters.
2. Make parse for whole

Note

Internally, javascript represents integers as 64-bit floating comma (52bits reserved for mantissa). This means that the above function can parse integers up to +/- 9007199254740992 (2 53).

Parse of numbers above 2 53 results in a loss of accuracy - that is, 0’s will be added. parseInt("90071992547409925") results in 90071992547409920

The alternative would simply be to return the result of replace (a string), without parsing for integer.

Answer 2

The leanest way I can imagine to do that:

"5tr1ng0".split("").filter(n => (Number(n) || n == 0)).join("");

or:

'5tr1ng0'.replace(/([^\d])+/gim, '');

or:

'5tr1ng0'.replace(/\D/gim, '');

Answer 3

I don’t know if my solution is better than the others, but it seems simpler, at least:

$string = "l337 5tr1ng";
$num    = parseInt($string.match(/\d/g).join(''));

The match looking for numbers (\d), non-stop at first found (flag g). As it returns the results as an array, you can give a join('') to put together everything I renew and parseInt if you wish to perform some mathematical operation with it.

If you just want to take all the numbers in an array, simply:

$num     = $string.match(/\d/g);

Answer 4

One way is parseInt(str.split(/\D+/).join(""), 10).

1. A regex \D+ takes everything that is not number;
2. Making split around this expression, we divide the string into "pieces" using this regex as the delimiter: ["5", "1", ""];
3. Making the join, we put her back together in a string: "51";
4. Finally the parseInt interprets the string as a number (at base 10; it is always important to specify the base, to avoid "zero left errors"): 51.

Example in jsFiddle. As for "more efficient", it will depend on your particular case (is a gigantic string? is a lot of small strings? etc), but the generic answer is "it doesn’t make much difference in practice"... (i.e. in most cases, the difference in performance between any "reasonable" solution will be negligible)

Answer 5

Simply remove all characters that are not numbers using the following regex:

string.replace(/\D/g, '') // substitui o que nao for numero por nada

Example:

var str = '(11) 2222-3333_4444_5555$6.777.-@8-!9';
var nums = str.replace(/\D/g, '');
console.log(nums);

Answer 6

You can use isNaN to check if the variable is not a number,

isNaN(num) // retorna true se num não contém num número válido

combined with the function filter, as follows

"5tr1ng".split('').filter(function(ele){
    return !isNaN(ele);
}).join(''); // retorna "51"

Answer 7

easiest way I found:

    function somenteNumeros(num) {
      var tecla = event.keyCode;
      return (tecla > 47 && tecla < 58)
    }

<input type="text" onkeypress="return somenteNumeros(this)"/>