search for a character in a string with javascript

Question

how to check if a javascript string doesn't contain characters like (#,$,/,@) because it's a username. I have a tried this code :

for(i=0;i<usrlength;i++) {
    if ($username.charAt(i)=='#'||$username.charAt(i)=='$') {
    }
}

but it's too long

Answer 1

Put all the special characters you want to exclude in a character set inside a regular expression:

const verify = username => !/[#\$\/@]/.test(username);
console.log(verify('foo'));
console.log(verify('foo#'));
console.log(verify('foo!'));
console.log(verify('f$oo'));

Answer 2

You can use regex to test the string with the desired pattern:

var pattern = /[$#@/]+/;
var username = "prachi.user";
var hasInvalidChar = pattern.test(username);
if (hasInvalidChar) {
  alert("Case 1 - Invalid");
} else {
  alert("Case 1 - Valid");
}


var pattern = /[$#@/]+/;
var username = "prachi.user#$@#/";
var hasInvalidChar = pattern.test(username);
if (hasInvalidChar) {
  alert("Case 2 - Invalid");
} else {
  alert("Case 2 - Valid");
}