仅当用户开始在输入字段中输入时，如何从输入值中删除某些警告文本？

Question

I have a value being php echoed in an input field after a form validation like so:

x - Confirm valid surname

What code (Javascript only) is appropriate to use if I want to remove the matching text " - Confirm valid surname" (this would be a warning message) when user starts typing inside the input field (ideally when changing to a valid surname)?

Answer 1

Did your "input" be like this?

<input value="<?php echo $errorMessage; ?>"/>

I advise to use the "placeholder" attribute,

<input placeholder="<?php echo $errorMessage; ?>"/>

or if you want to keep using JS,

var inputBox = document.getElementById(INPUT_BOX_ID);
inputBox.oninput = function(){
    inputBox.value = inputBox.value.replace(" - Confrim valid surname",""); // Simply remove the Error Text you've echoed
    inputBox.oninput = null; //  Delete the function so user can type something
}
// Its still not detecting the valid surname, but its removes the " - Confrim valid surname"