For this specific example,

 var thenum = thestring.replace(/^\D+/g, ''); // Replace all leading non-digits with nothing

In the general case:

 thenum = "foo3bar5".match(/\d+/)[0] // "3"

Here's a bonus: regex generator.

function getre(str, num) {
  if(str === num)
    return 'nice try';
  var res = [/^\D+/g,/\D+$/g,/^\D+|\D+$/g,/\D+/g,/\D.*/g, /.*\D/g,/^\D+|\D.*$/g,/.*\D(?=\d)|\D+$/g];
  for(var i = 0; i < res.length; i++)
    if(str.replace(res[i], '') === num)
      return 'num = str.replace(/' + res[i].source + '/g, "")';
  return 'no idea';
};

function update() {
  $ = function(x) { return document.getElementById(x) };
  var re = getre($('str').value, $('num').value);
  $('re').innerHTML = 'Numex speaks: <code>' + re + '</code>';
}

<p>Hi, I'm Numex, the Number Extractor Oracle.
<p>What is your string? <input id="str" value="42abc"></p>
<p>What number do you want to extract? <input id="num" value="42"></p>
<p><button onclick="update()">Insert Coin</button></p>
<p id="re"></p>

+myString.replace(/[^\d.ex-]+/gi, '')

strips out all characters that cannot appear in a JavaScript number, and then applies the + operator to it to convert it to a number. If you don't have numbers in hex format or exponential format then you can do without the ex.

EDIT:

To handle locales, and handle numbers in a more tailored way, I would do the following

// Get rid of myriad separators and normalize the fraction separator.
if ((0.5).toLocaleString().indexOf(',') >= 0) {
  myString = myString.replace(/\./g, '').replace(/,/g, '.');
} else {
  myString = myString.replace(/,/g, '');
}

var numericValue = +(myString.match(
    // Matches JavaScript number literals excluding octal.
    /[+-]?(?:(?:(?:0|[1-9]\d*)(?:\.\d*)?|\.\d+)(?:e[+-]?\d+)?|0x[0-9a-f]+)/i)
    // Will produce NaN if there's no match.
    || NaN);

This is a great use for a regular expression.

    var str = "Rs. 6,67,000";
    var res = str.replace(/\D/g, "");
    alert(res); // 667000

\D matches a character that is not a numerical digit. So any non digit is replaced by an empty string. The result is only the digits in a string.

The g at the end of the regular expression literal is for "global" meaning that it replaces all matches, and not just the first.

This approach will work for a variety of input formats, so if that "Rs." becomes something else later, this code won't break.

Try match()

var text = "top 50 right 100 left 33";
var arr = text.match(/[0-9]{1,3}/g);
console.log(arr); //Returns an array with "50", "100", "33"

You can also use [\d+] (digits) instead of [0-9]

Correct way:

var str = '12  3   44 5 \n 7 88';
//if there matches, store them into the array, otherwise set 'numbers' to empty array
var numbers = str.match(/\d+/g)?str.match(/\d+/g):[];
//to convert the strings to numbers
for(var i=0;i<numbers.length;i++){
    numbers[i]=+numbers[i]
}
alert(numbers);

Why? .match() is just an easier thing to use there. \d+ gets a number of any length, flag g returns all the matches, not only the first match.

If you also want to match the floats, the regex would be /\d+([\.,]\d+)?/g. It'll also match 42,12 or 42.12.

var result= "1 banana + 1 pineapple + 3 oranges";
result.match(/[0-9]+/g)

Here's an example function that will return an array representing the two numbers, or null if there wasn't a match:

function extractNumbers(str) {
    var m = /(\d+)to(\d+)/.exec(str);
    return m ? [+m[1], +m[2]] : null;
}

You can adapt that regular expression to suit your needs, say by making it case-insensitive: /(\d+)to(\d+)/i.exec(str).

You could use a regular expression for it. It looks only for connected numbers.

console.log('(235+456+2+3-6-(2*5))'.match(/\d+/g));

You can get it like this:

var suffix = 'comment_like_123456'.match(/\d+/); // 123456

With respect to button:

$('.comment_like').click(function(){
  var suffix = this.id.match(/\d+/); // 123456
});

How about a simple regexp

s.replace(/[^\d]/g, '')

or as stated in the comments

s.replace(/\D/g, '')

http://jsfiddle.net/2mguE/

This will get all the numbers separated by coma:

var str = "10 is smaller than 11 but greater then 9";
var pattern = /[0-9]+/g;
var matches = str.match(pattern);

After execution, the string matches will have values "10,11,9"

If You are just looking for thew first occurrence, the pattern will be /[0-9]+/ - which will return 10

(There is no need for JQuery)

You can use a regex to get the first integer :

var num = parseInt(str.match(/\d+/),10)

If you want to parse any number (not just a positive integer, for example "asd -98.43") use

var num = str.match(/-?\d+\.?\d*/)

Now suppose you have more than one integer in your string :

var str = "a24b30c90";

Then you can get an array with

var numbers = str.match(/\d+/g).map(Number);

Result : [24, 30, 90]

For the fun and for Shadow Wizard, here's a solution without regular expression for strings containing only one integer (it could be extended for multiple integers) :

var num = [].reduce.call(str,function(r,v){ return v==+v?+v+r*10:r },0);

Just use a simple regex:

const input = 'this is a signal , entry : 2430 and side is short'; 

const number1 = input.match(/entry\W+(\d+)/)?.[1]; // "2430"

const number2 = input.match(/santa\W+(\d+)/)?.[1]; // undefined

Your RegEx works, if you want single digit right after /

Your regex \d+\/(\d)\d\d\d will match digits / then four digits and add first digit after slash in captured group. Note that 0th captured group will contain complete matched string. g flag is not necessary as there is only one instance of numbers in that pattern.

You can use this regex, but use first index to get the digit right after slash.

'1/2009'.match(/\d+\/(\d)\d\d\d/g)[1]
                                   ^  : Get me the value from first captured group.

And this regex can be optimized to below

.match(/\/(\d)/)[1]

This will match the number followed by /. And use the first captured group to extract the number.

<input type="text" onblur="console.log(this.value.match(/\/(\d)/)[1])" />

To get all digits after /

Just add + quantifier to \d in the captured group.

.match(/\/(\d+)/)[1]

I used the following regexp to extract numbers from a string:

var string = "border-radius:10px 20px 30px 40px";
var numbers = string.match(/\d+/g).map(Number);

var str = "text-345-3535"

var arr = str.split(/-/g).slice(1);

Try it out: http://jsfiddle.net/BZgUt/

This will give you an array with the last two number sets.

If you want them in separate variables add this.

var first = arr[0];
var second = arr[1];

Try it out: http://jsfiddle.net/BZgUt/1/

EDIT:

Just for fun, here's another way.

Try it out: http://jsfiddle.net/BZgUt/2/

var str = "text-345-3535",first,second;

str.replace(/(\d+)-(\d+)$/,function(str,p1,p2) {first = p1;second = p2});

Yes, match is the way to go:

var matches = str.match(/(\d+)sl(\d+)/);
var number1 = Number(matches[1]);
var number2 = Number(matches[2]);

If you want to not include the dot, a look-ahead would make sense:

/[-+]?\d*(\.(?=\d))?\d+/g

Another option is to move the second \d+ inside the parentheses:

/[-+]?\d+(\.\d+)?/g

Your data is not in a good format. You would need an array of arrays of numbers, not an array of strings. So the first task is to make that conversion.

Then you could use the distance formula to calculate the distance to the given coordinates, and store that as an extra information with each point in the list.

Then sort by that additional distance. Sorting it is not the most efficient method, as you could retrieve the minimum distance first, then retrieve the minimum after removing the first, and finally retrieve the minimum again after removing the first minima found. But if you are interested in such optimisation, have a try yourself.

After sorting, slice the first three elements out of the resulting array and return that. You may want to convert those three items back to the original format, i.e. an array of three strings.

Here is a snippet:

function closestThree(data, px, py) {
    return data
        .map( s => s.split(',').map(Number) ) // Convert to pairs of numbers
        .map( ([x,y]) => [x,y,(x-px)*(x-px)+(y-py)*(y-py)] ) // Add squared distance
        .sort( (a, b) => a[2] - b[2] ) // Sort by distance
        .slice(0, 3) // Get three first results
        .map( ([x, y]) => x + ',' + y ); // Convert back to strings
}

// Sample
const points = ['123,5432', '432,325', '735,1045', '583,564'];
const res = closestThree(points, 405, 630);
console.log(res);

You could use a regex:

var foo = '2x32';
var matches = foo.match(/^(\d+)x(\d+)$/);
if (matches.length > 2) {
    var a = matches[1]; // = 2
    var b = matches[2]; // = 32
}