JAVASCRIPT

check if a string is alphanumeric

 if (string.match(/^[0-9A-Za-z]+$/) === null) { 
 //is not alphanumeric
 }else{
 //it is alphanumeric
 }

java code to check if string is alphanumeric

java.util.regex.*;
class AlphanumericExample
{
  public static void main(String...s)
  {
    String s1="adA12", s2="jh@l";
    System.out.println(s1.matches("[a-zA-Z0-9]+"));
    System.out.println(s2.matches("[a-zA-Z0-9]+"));
  }
}

python check if a character is alphanumeric

for i in s:
    if i.isalnum():
        print(True)
        break