我有一个登录页面。 我想在表单中添加多个操作，或者有另一种解决方案

Question

I have a login page and I have a php & javascript page. I want to link form to javascript and php code html loin page

<form action="INDEX.PHP" method="POST" class="two">
    <div>
        <button class="yeu"  id="submit" type="submit" name="submit" onclick="validate();validatewoman();validateuser();">login</button>
        <input type="text" name="username" id="username" maxlength="14">
    </div>
    <div id="user" style="color: black; font-size: 20px; text-align: left;">
        <pre style="color: black; font-size: 20px; text-align: left; display: none;"></pre>
</form>

php

<?php
$conn = mysqli_connect('localhost','root','root','login');
if(!$conn){
    echo "data base error";
}
if (isset($_POST['submit'])){
$username = $_POST['username'];
    $sql = "INSERT INTO login_table(login) VALUES ('$username')";
   if(!mysqli_query($conn , $sql)){
       echo 'error: '. mysqli_error($conn);
} 
}
?>

javascript

function validate(){
    var user_one = document.getElementById("username").value;
    if (
        user_one=== "578815452122"
    ){
    else{
document.write = "user error" ; 
    };

}; 

Answer 1

You can use the onsubmit Event Listener , like this:

const myform = document.getElementsByClassName('two')[0];

function validate (e) { ... }

myform.addEventListener('submit', validate);

When someone tries to submit your form, the event listener will detect the submit event and run the validate() function.

The form will be submitted only after the function has run.

---

NB When declaring your validate() function, you should have the event object specifically named as a parameter (eg. function validate (event) {...} or function validate (e) {...} ), such that at any point where you would like the form to not submit, you can invoke event.preventDefault(); or e.preventDefault(); .

See:

• https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault