Javascript / html / php自动错误检查[关闭]

Question

I'm pretty new to HTML and i was wondering if there was a way to have constant/instant error checking on forms.

So for example there is a user putting in a username. the username must be at least 5 characters but no more then 15. If the user hasn't entered any data an error will appear on the screen (not a popup) once the user has input 5-15 characters the error will disappear.

I was wondering how i could go about making this happen rather then having to have the user hit submit every time to check the form for errors. I can use JavaScript (since that's what I've used to do other error checking) to some degree and i'd prefer to not use php but i will if it's necessary to complete this.

So i'm wondering where someone can point me in the right direction in order to read about this or provide me with the function in order to have it automatically detect errors.

If you have any questions or need more information let me know! i'll do my best to provide it. Sorry if it's a little ambiguous.

http://imgur.com/a/d9n5X

I've provided images on what it could possibly look like. So the first image an error appears due it not fitting the requirements of 5-15 characters. The second image fits it so the error disappears. I hope this helps!

Thanks in advance!

Answer 1

Data form validation would be the best way to accomplish this.

<form>
  <label>
    Restricted Input
    <input pattern=".{5,15}" required title="Value must be between 5 and 15 characters." />
  </label>
  <label>
    Unrestricted Input
    <input />
  </label>
  <input type="submit" value="Submit" />
</form>

</div>