How to validate input for only email friendly characters?-CodePudding

I have JavaScript that validates whole email once entered:

function ValidateEmail(inputText)
{
    var mailformat = /^[a-zA-Z0-9.!#$%&’* /=?^_`{|}~-] @[a-zA-Z0-9-] (?:\.[a-zA-Z0-9-] )*$/
    if(inputText.value.match(mailformat))
    {
        alert("This is not a valid email address");
        return false;
        }
}

But how to check if single character is valid for email? So I want to prevent users to enter bad email characters. So function param would be these and should return false only if invalid character present:

m
my
mya
....
myaddress
....
myaddress@mail.com

CodePudding user response：

great answer: https://stackoverflow.com/a/46181/3764369

issues follows RFC 5322 https://emailregex.com/

w3 code example:

function ValidateEmail(inputText)
{
  var mailformat = /^\w ([\.-]?\w )*@\w ([\.-]?\w )*(\.\w{2,3}) $/;
  if(inputText.value.match(mailformat))
  {
    alert("Valid email address!");
    document.form.email.focus();
    return true;
  }
  else
  {
    alert("You have entered an invalid email address!");
    document.form.email.focus();
    return false;
  }
}

CodePudding user response：

You could test the individual characters your user submits with a function like this one shown below, since the allowable characters are limited to letters (a-z), numbers, underscores, periods, and dashes.

/* function that validates input for only email friendly characters */
function validateEmailChars(input) {
  var validCharacters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789@._-';
  for (var i = 0; i < input.length; i  ) {
    if (validCharacters.indexOf(input[i]) === -1) {
      return false;
    }
  }
  return true;
}

   
var testString1 = 'm'
var testString2 = 'my'
var testString3 = 'mya';
var testString4 = '[email protected]';

console.log(validateEmailChars(testString1));
console.log(validateEmailChars(testString2));
console.log(validateEmailChars(testString3));
console.log(validateEmailChars(testString4));
//should all return true

var testString5 = '[email protected]';

console.log(validateEmailChars(testString5));
//should return false