Question

In JavaScript, what would be the regular expression for a number followed by a word? I need to catch the number AND the word and replace them both after some calculation.

Here are the conditions in a form of example:

123 dollars => Catch the '123' and the 'dollars'.
foo bar 0.2 dollars => 0.2 and dollars
foo bar.5 dollar => 5 and dollar (notice the dot before 5)
foo bar.5.6 dollar => 5.6 and dollar
foo bar.5.6.7 dollar => skip (could be only 0 or 1 dot)
foo bar5 dollar => skip
foo bar 5dollar => 5 and dollar
5dollar => 5 and dollar
foo bar5dollar => skip

• Of course 123.555, 0.365, 5454.1 are numbers too.

• For making things simpler the word is a specific one (e.g
  dollar|euro|yen).

• OK.. Thank you all… Here is the basic function I made so far:

  var text = “foo bar 15 dollars. bla bla..”;
  var currencies = {
  dollars: 0.795
  };

  document.write(text.replace(/\b((?:\d+.)?\d+) *([a-zA-Z]+)/, function(a,b,c){
  return currencies[c] ? b * currencies[c] + ‘ euros’ : a;
  }
  ));

Answer 1

Try this:

/\b(\d*\.?\d+) *([a-zA-Z]+)/

That will also match stuff like .5 tests. If you don’t want that, use this:

/\b((?:\d+\.)?\d+) *([a-zA-Z]+)/

And to avoid matching “5.5.5 dollars”:

/(?:[^\d]\.| |^)((?:\d+\.)?\d+) *([a-zA-Z]+)/