What is the 'instance-id' field?

Issue

• What is the instace-id or instanceId field and what is it used for?

Environment

• All Liferay versions

Resolution

• It's a random alphanumeric value.
• Liferay uses this value to be able to identify the field uniquely.
• Actual generation sample code:
  • JS (fieldSupport.js)

    export function generateInstanceId(isNumbersOnly) {
      return Math.random()
        .toString(isNumbersOnly ? 10 : 36)
        .substr(2, 8);
    }

  • Java (StringUtil.randomString() method is used)

    public static String randomString(int length) {
      Random random = new Random();
    
      char[] chars = new char[length];
    
      for (int i = 0; i < length; i++) {
        int index = random.nextInt(_RANDOM_STRING_CHAR_TABLE.length);
    
        chars[i] = _RANDOM_STRING_CHAR_TABLE[index];
      }
    
      return new String(chars);
    }

Additional Information

• Sometimes it is used to generate the field ID, which must also be unique. As per the W3C DOM#getElementById()
  
  • If more than one element has an ID attribute with that value, what is returned is undefined.