javascript regex optional minus

问题

I have the following function in javascript:

function unString(String){     
   var justNumbers = /(?=.*\d)\d*(?:\.\d*)?/;
   var result      = String.match(justNumbers);
   result *= 1;
   result = Math.round(result*100) / 100;
   return result;
}

The meaning of it is to extract the number out of every possible css value, so that it can be added or substracted or multiplied with other values: e. g.

var newPadding = unString(  $('#myID').css("padding-bottom")  )*10 + "px";

Having modified my code I would now need the regex to allow an optional minus, to allow values like "-3px" be transformed to "-3" (actually the function can't and returns "0").

[I know there are tons of optional minus regex threads on stackoverflow and other forums, but they don't match the form of my regex - I do not have much experience with regex, for creating the above one I had to do long and intense research - and so I could not modify my regex, referring to these]

[The regex is should allow digits, optional decimal point and optional minus]

Thx in advance

回答1:

You can use

/-?[0-9]*\.?[0-9]+/g

See the regex demo

Explanation:

• -? - an optional hyphen (you may replace it with [-+]? to match both - and + optionally)
• [0-9]* - zero or more digits
• \.? - an optional dot
• [0-9]+ - 1 or more digits.

来源：https://stackoverflow.com/questions/38523118/javascript-regex-optional-minus