Trying the regex very hard but could not get the desired result.

1. Must begin with numbers and maximum of 4
2. followed by only one allowed alphabet

Please have a look at below code.

var strings = [
 '1h', //should match
 '13s', //should match
 '30m', //should match
 '42hr', //should not match
 '8   hours  ', //should not match
 '765765', //should not match
 '5sec', //should not match
 '23445345345s', //should not match
 '335m' //should match
];

for (var i = 0; i < strings.length; i  ) 
{
    var match = strings[i].match(/\d{4}[h|m|s]{1}/g);
  console.log(strings[i], (match ? "Match" : "Not match"));
}

CodePudding user response：

You regex should be:

/^\d{1,4}[hms]$/gm

First, you require 4 digits with d{4}

Change it to d{1,4} to be one to four digits

Then add a $ to indicate the end of the string, so it doesn't allow more characters after the letter

Check out Regex101, Really useful for testing and understanding regex

CodePudding user response：

I've added a ^ to match from start

strings.filter(x =>  x.match(/^\d{1,4}[hms](?!\w)/g)  )