正则表达式检查浮点数 -> 不以小数点结尾和星号

Question

I am facing issues with regex pattern for Float number -> that should not end or stars with decimal points..

I have tried following regex patter.. that is

regex = /^\d*\.?\d*$/

// on doing

regex.test(11.) 
regex.test(.11) 

// it is returning true in checking

// I need to make this as false, comment will be much helpful thank you.

Answer 1

You should bear in mind that regex only works with strings. When you pass a non-string variable as input to a RegExp , it will first coerce it to a string type.

Have a look:

 console.log(11. , 'and', .11); // => 11 and 0.11

So, the actual string values you pass to your ^\d*\.?\d*$ regex are 11 and 0.11 that can be matched with the given pattern. Actually, ^\d*\.?\d*$ is a regex that is usually used for a very loose live number input validation, eg see How to make proper Input validation with regex? .

What you want is to implement a final, on-submit validation pattern, so that it could not pass strings like 11. and .11 . There have been lots of threads discussing this kind of regex:

• Regular expression for floating point numbers
• regular expression for finding decimal/float numbers?

Basically, for validation, you will need something like

/^\d+(?:\.\d+)?$/.test(input_string)
/^[0-9]+(?:\.[0-9]+)?$/.test(input_string)
/^[0-9]+(?:\.[0-9]{1,2})?$/.test(input_string)  // Some need to only allow 1 or 2 fractional digits
/^[0-9]{1,3}(?:\.[0-9]{2})?$/.test(input_string) // 1-3 digits in the integer part and two required in the fractional part