CODEWITHSUNDEEP
javascriptregex
JZ.
JZ.

Reputation: 21877

javascript regular expression

How do you write a JS regular expression to extract the first "2" from "/?page=2&promo_id=1234". (ie page number 2)

Thanks!

Upvotes: 0

Views: 106

Answers (4)

Thomas Hupkens
Thomas Hupkens

Reputation: 1590

It depend on what may vary in your string. If the number is the only variable, then:

var match, pageNumber;
if(pageNumber = "/?page=2&promo_id=1234".match(/page=(\d+)/))
    pageNumber = match[1];

Or the ugly (but shorter) way

var pageNumber = ("/?page=223&promo_id=a".match(/page=(\d+)/)||[,undefined])[1]

Upvotes: 1

maerics
maerics

Reputation: 156384

var extractPageNumber = function(s) {
  var r=/page=(\d+)/, m=(""+s).match(r);
  return (m) ? Number(m[1]) : undefined;
};
extractPageNumber("/?page=2&promo_id=1234"); // => 2
extractPageNumber("/?page=321&promo_id=1234"); // => 321
extractPageNumber("foobar"); // => undefined

Upvotes: 1

Nick Brunt
Nick Brunt

Reputation: 10047

I wouldn't use regular expressions as such, I'd use the split method:

var str="/?page=2&promo_id=1234";

document.write(str.split("/?page=")[1][0]);

Of course this will only work for single digit numbers. You could modify it to work for all numbers using a proper regular expression.

http://jsfiddle.net/u8ZXc/

Upvotes: 0

Z. Zlatev
Z. Zlatev

Reputation: 4820

This should do the trick. 

var match = /page=(\d+)/.exec("/?page=2&promo_id=1234"), pageNum = match[1];

Upvotes: 2

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