Pattern matching for actual numbers using regex

I have a question out of my own curiosity. Although I have a working solution, I am interested to know why one method is successful while the other isn't.

I was in need of a regular expression for validating if a user input is a valid number. Here are some examples:

87

887.65

-87

-87.65

My initial attempt was like this: 

^(\-?[0-9]+(\.[0-9]*)?)$

It worked well, but it accepted strings like '7x', '1a', '89p' which were not desired. My updated solution is as follows and seems to be working correctly:

^(\-?[0-9]+(\.[0-9]+)?)$

The second one (with the '+') is more concise, yet I'm unsure why the first one allowed letters and the second did not. Can anyone see what I might be overlooking?

javascriptangularjsregexng-pattern

Answer №1

When using regex, be sure to escape certain characters like "." in order to match them literally. Otherwise, the regex will match any character instead. Additionally, the "+" operator requires at least one occurrence of a decimal, ensuring that it won't match patterns like "7x", but will match patterns like "7x1". Check out this Regex demo for more information.

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