Match a string(input text from user) with regular expression

Question

I have a requirement where there is a customet name text box and the user able to input customer name to search customer. And the condition is user can add do wild card search putting * either infront or after the customer name. And the customer name should be minimum three characters long. I am using Regex to validate the user entry. Now in case the input is like "*aaa*" .. I am validate this type of input using the following regex :

[*]{1}([a-z]|[A-Z]|[0-9]){3,}[*]{1}

The code is like below:

    var str = "*aaa*";
    var patt = new RegExp("[*]{1}([a-z]|[A-Z]|[0-9]){3,}[*]{1}");
    var res = patt.test(str);  
    alert(res);

    var str = "*aaa***";
    var patt = new RegExp("[*]{1}([a-z]|[A-Z]|[0-9]){3,}[*]{1}");
    var res = patt.test(str);  
    alert(res);

    var str = "*aaa*$$$$";
    var patt = new RegExp("[*]{1}([a-z]|[A-Z]|[0-9]){3,}[*]{1}");
    var res = patt.test(str);  
    alert(res);

Now for the input "*aaa*" res is coming true. But for this type of inputs also "*aaa**", "*aaa*$" its comimg true. And this expected as these expressions also contains the part( *aaa*) which satisfies the regex.But these inputs("*aaa**", *aaa*$** etc. ) are wrong.

Please let me know where I am doing wrong ? is there any issue with the regex or the way checking is wrong ?

vks · Accepted Answer · 2015-05-28 06:10:13Z

2

^(?:[*]([a-z]|[A-Z]|[0-9]){3,}[*])$

Use anchors ^$ to disable partial matching.See demo.

https://regex101.com/r/tS1hW2/17

answered May 28, 2015 at 6:10

vks

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3 Comments

Sambuddha Over a year ago

Could you please explain me what changes u did... ^$ these u used so that the whole string is matched againts the regex. But why u have used ?:

vks Over a year ago

@Sambuddha when you dont use ^$ regex will make partial matches .from *aaa** it will match *aaa* and pass.When you add anchors it wont unless complete string is matched

Wiktor Stribiżew Over a year ago

I guess ^[*][a-zA-Z0-9]{3,}[*]$ is a much better way to write this regex. With i option, it is even shorter: /^[*][a-z0-9]{3,}[*]$/i.

Ja͢ck · Accepted Answer · 2015-05-28 07:37:01Z

1

The string *aaa*$$$ contains a segment of *aaa*, so it will yield true; to match against the whole string you need to add anchors on both sides. The $ and ^ anchors assert the start and end of the subject respectively.

Also, you can simply the expression greatly by using a character class trick. The \w is comprised of [0-9a-zA-Z_], and we only don't want the underscore, so we can use a negative character class with the opposite of \w (which is \W) and an underscore; I agree, it takes some mental power ;-)

var str = "*aaa*$";
    var patt = /^\*[^\W_]{3,}\*$/;
    var res = patt.test(str);  
    alert(res); // false

Alternatively, you can merge all your character classes together into one like so:

[A-Za-z0-9]

edited May 28, 2015 at 7:37

answered May 28, 2015 at 6:20

Ja͢ck

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