Develop Reference

Regex - Output character not valid

I'm trying to create a function to check if a field is valid based on a set of characters and, if not, output which ones are not allowed. Don't know if it is the best approach, but basically instead of telling the user which ones he can use, I want to tell which ones he can't.
function allowedString(field){
var validCharacters = new RegExp('^[a-zA-Z0-9áéíóúÁÉÍÓÚñÑ_-¿?¡!.,;:$() ]*$');
if(!validCharacters.test(field.val())){
var invalid = ?;
return "Invalid characters: "+invalid;
}
}

Using your character set in your regex, you can remove all those characters from the string and resultant will be the non-allowed characters. Try this JS codes,
function allowedString(s){
var validCharacters = new RegExp('^[a-zA-Z0-9áéíóúÁÉÍÓÚñÑ_-¿?¡!.,;:$() ]*$');
if(!validCharacters.test(s)){
var invalid = s.replace(/[a-zA-Z0-9áéíóúÁÉÍÓÚñÑ_-¿?¡!.,;:$() ]*/g,'');
return "Invalid characters: "+invalid;
} else {
return "All characters are valid"; // return any message you want
}
}
console.log(allowedString('aa##bb##'));
console.log(allowedString('abc'));
console.log(allowedString('aa##bb##~~^^'));
And change your field parameter in function back to your original code.

You can split the string and deal with it as with an array (not sure about the performance, though).
function allowedString(field){
const validCharacters = new RegExp('^[a-zA-Z0-9áéíóúÁÉÍÓÚñÑ_-¿?¡!.,;:$() ]*$');
const disallowed = field.val().split('').filter(x => !validCharacters.test(x));
if (disallowed.length) {
return disallowed.join('');
}
}

I'd reverse the test: Is there an invalid character within the string?
Take care you have to escape the dash in a character class except in first and last position.
function allowedString(field){
var invalidCharacters =/([^a-zA-Z0-9áéíóúÁÉÍÓÚñÑ_\-¿?¡!.,;:$() ])/;
invalid = invalidCharacters.exec(field);
if (invalid != null) {
return "Invalid characters: "+invalid[1];
} else {
return "OK";
}
}
console.log(allowedString('abc'));
console.log(allowedString('abc#def'));
console.log(allowedString('abc§def'));

validation function doesn't work

I have created a java script function, it should validate the input character that should contain 10 characters and can contain alphanumeric characters, but this function does not work, please help me
function ValidateNIC(id)
{
var letters = /^[0-9a-zA-Z ]+$/;
while(id.value.length==10)
if(id.value.match(letters))
{
return true;
}
else
{
alert('NIC must have alphanumeric characters only or should contain 10 charaters');
id.focus();
return false;
}
}

With your code as it stands, if the length is not 10, then nothing else happens. A better approach might be:
if ((id.value.length == 10) && id.value.match(letters)) {
return true;
}
alert("NIC must ...");
id.focus();
return false;

You can put all the conditions for validation in Regex like ^[a-zA-Z0-9]{10}$. Note that additional {10} in the regex pattern string for creating a match only when the length is 10 exactly.
Then you can make use of the Regex Object test method, which test the regex pattern against a string and returns true if the match is successful and false otherwise.
Complete modified snippet below with positive and negative test cases.
function ValidateNIC(id){
var aphaPattern10 = /^[a-zA-Z0-9]{10}$/g;
var result = aphaPattern10.test(id.value);
if(!result){
alert('NIC must have alphanumeric characters only or should contain 10 charaters');
//id.focus();
}
return result;
}
var testObjPass = { value : "012345678a"}
console.log(ValidateNIC(testObjPass));
var testObjFail = { value : "012345678a21312"}
console.log(ValidateNIC(testObjFail));

The following code checks the following
NIC must have alphanumeric characters only or should contain 10 charaters.
So if it is only 10 characters then it will not alert else, it will test the regex. Considering id is an object with key value
function ValidateNIC(id)
{
var letters = /^[0-9a-zA-Z ]+$/;
if(id.value.length!==10){
if(id.value.match(letters))
{
return true;
}
else
{
alert('NIC must have alphanumeric characters only or should contain 10 charaters');
id.focus();
return false;
}
}
}

Regular expression for numbers only

I am using the following code to detect if a string is a number:
var numberPattern = /[a-zA-Z]/;
if (!numberPattern.test($(this).text())) {
numberSort = true;
} else {
numberSort = false;
return numberSort;
}
But i have something like "(123)" and it detects it as number. Can somebody help me to update the regex to detect the paranthesys too?
I have tried: /[a-zA-Z]/(/)/ but does not work.

Use \d for matching digit and start and end anchors to check entire string.
var numberPattern = /^\d+$/;
return numberPattern.test($(this).text());

javascript code to check special characters

I have JavaScript code to check if special characters are in a string. The code works fine in Firefox, but not in Chrome. In Chrome, even if the string does not contain special characters, it says it contains special characters.
var iChars = "~`!#$%^&*+=-[]\\\';,/{}|\":<>?";
for (var i = 0; i < chkfile.value.length; i++)
{
if (iChars.indexOf(chkfile.value.charAt(i)) != -1)
{
alert ("File name has special characters ~`!#$%^&*+=-[]\\\';,/{}|\":<>? \nThese are not allowed\n");
return false;
}
}
Suppose I want to upload a file desktop.zip from any Linux/Windows machine.
The value of chkfile.value is desktop.zip in Firefox, but in Chrome the value of chkfile.value is c://fakepath/desktop.zip. How do I get rid of c://fakepath/ from chkfile.value?

You can test a string using this regular expression:
function isValid(str){
return !/[~`!#$%\^&*+=\-\[\]\\';,/{}|\\":<>\?]/g.test(str);
}

Try This one.
function containsSpecialCharacters(str){
var regex = /[ !##$%^&*()_+\-=\[\]{};':"\\|,.<>\/?]/g;
return regex.test(str);
}

Directly from the w3schools website:
var str = "The best things in life are free";
var patt = new RegExp("e");
var res = patt.test(str);
To combine their example with a regular expression, you could do the following:
function checkUserName() {
var username = document.getElementsByName("username").value;
var pattern = new RegExp(/[~`!#$%\^&*+=\-\[\]\\';,/{}|\\":<>\?]/); //unacceptable chars
if (pattern.test(username)) {
alert("Please only use standard alphanumerics");
return false;
}
return true; //good user input
}

Did you write return true somewhere? You should have written it, otherwise function returns nothing and program may think that it's false, too.
function isValid(str) {
var iChars = "~`!#$%^&*+=-[]\\\';,/{}|\":<>?";
for (var i = 0; i < str.length; i++) {
if (iChars.indexOf(str.charAt(i)) != -1) {
alert ("File name has special characters ~`!#$%^&*+=-[]\\\';,/{}|\":<>? \nThese are not allowed\n");
return false;
}
}
return true;
}
I tried this in my chrome console and it worked well.

You could also do it this way.
specialRegex = /[^A-Z a-z0-9]/
specialRegex.test('test!') // evaluates to true
Because if its not a capital letter, lowercase letter, number, or space, it could only be a special character

If you don't want to include any special character, then try this much simple way for checking special characters using RegExp \W Metacharacter.
var iChars = "~`!#$%^&*+=-[]\\\';,/{}|\":<>?";
if(!(iChars.match(/\W/g)) == "") {
alert ("File name has special characters ~`!#$%^&*+=-[]\\\';,/{}|\":<>? \nThese are not allowed\n");
return false;
}

Checking form for special characters in JavaScript.

I am trying to make a function that checks for special characters such as !##$%^&*~ when I input a password. I've been using regular expressions to check for everything else, but does anyone know how I can make it so the function checks the password for at least one of these special characters?
Here's what I have:
function validateEmail(email)
{
var emailPattern = /^[a-zA-Z0-9._-]+#[a-zA-Z0-9.-]+\.[a-zA-Z]{2,3}$/;
return emailPattern.test(email);
}
function validatePassword(password)
{
var passwordPattern = /(?=.*\d)(?=.*[a-z])(?=.*[A-Z])./;
return passwordPattern.test(password)
}
function validate()
{
var email = user.email.value;
if(validateEmail(user.email.value))
user.validEmail.value = "OK";
else
user.validEmail.value = "X";
if(validatePassword(user.password.value))
user.validPassword.value = "OK";
else
user.validPassword.value = "X";
}

You can match any non-(letters, digits, and underscores) characters with \W.
So to check the password if has any special character you can just simply use:
if (password.match(/\W/)) {
alert('you have at least one special character');
}
to use it in your function you can replace the whole regex with:
var passwordPattern = /^[\w\W]*\W[\w\W]*$/;
that will return true if the string has at least one special character.