Regular Expression still allowing decimal at the end

Question

Hey Everyone I'm working in angular and I am trying to create a filter that just allows numbers in the format of "any amount of digits . any amount of digits" Otherwise is will prevent the entry if it's not in the format of [0-9.]. The pattern is still allowing numbers like this 000.00. in the input field.

How do I stop it from inserting that last decimal point? Thank you for your assistance ahead of time!

code

$scope.filterValue = function($event, value){
    var char = String.fromCharCode($event.keyCode);
    if(value === null){
        if(isNaN(char)){
            $event.preventDefault();
        }
    }else{  
        var pattern = /^-?[0-9]{0,}\.?[0-9]{0,}$/;
        if(pattern.test(value)){
            if(isNaN(char) && (value.indexOf(".") == value.length-1)){
                $event.preventDefault();
            }
        }else{
             $event.preventDefault();
        }
    }
};

Do you require _exactly_ two numbers after the dot, or any amount of numbers? — VLAZ, Sep 14 '16 at 21:29

VLAZ · Answer 1 · 2016-09-14T21:55:24.893

I will reference an article on floating point and regex which was written by people way smarter than me. Here is the regex suggested there:

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

And an explanation - it defines both the optional and the mandatory input. In this case you want to have at least one digit which is the final [0-9]+ but you also allow for more digits and an optional dot character. The regex also allows a number to start with a + or a -

See this in regex101

var regex = /^[-+]?[0-9]*\.?[0-9]+$/;

var test = function(input) {
  console.log("Testing ["+ input + "]. Result: " + (regex.test(input) ? "passes" : "fails"));
}

//valid
test("1");
test("2.1");
test("3.14");
test("-4");
test("+5");
test(".6");
test("-.7");
test("+.8");

//invalid
test(""); // yes - empty string
test(".");
test("-");
test("+");
test("-.");
test("+.");
test("9.");
test("10..1");
test("11.1.2");
test(".12.1");
test("..13");
test("-.14.");
test("+..15");

KrishCdbry · Answer 2 · 2016-09-14T21:46:38.397

0

$scope.filterValue = function($event, value){
var char = String.fromCharCode($event.keyCode);
if(value === null){
    if(isNaN(char)){
        $event.preventDefault();
    }
}else{  
    var pattern = /^-?([0-9]{1,})(?:\.[0-9]+)?$/;
    if(pattern.test(value)){
        if(isNaN(char) && (value.indexOf(".") == value.length-1)){
            $event.preventDefault();
        }
    }else{
         $event.preventDefault();
    }
}
};

Try this one

var regex = /^-?([0-9]{1,})(?:\.[0-9]+)?$/;

edited Sep 14 '16 at 21:46

answered Sep 14 '16 at 21:33

KrishCdbry

1,049
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What's the point of `(...)+` for the part before the separator? – Ingo Bürk Sep 14 '16 at 21:34
Good one ! Nice observation I skipped – KrishCdbry Sep 14 '16 at 21:36

score 0 · Answer 3 · answered Sep 15 '16 at 01:49

These regex should cover what you probably need.
The overall assumption is there has to be input so we use
an alternation to positively check the forms.

This doesn't require a dot

^-?(?:\d+(?:\.\d*)?|\.\d+)$

 ^ 
 -?
 (?:
      \d+                  # Digits 
      (?: \. \d* )?        # Optional  ( dot, optional ( digits ) )
   |                     # or,
      \. \d+               # Dot, digits 
 )
 $

This requires a dot

^-?(?:\d+\.\d*|\.\d+)$

 ^ 
 -?
 (?:
      \d+                  # Digits 
      \. \d*               # Dot, optional digits 
   |                     # or,
      \. \d+               # Dot, digits 
 )
 $

Regular Expression still allowing decimal at the end

3 Answers3