创建高效的 function 而不是重复的函数

Question

I have a function which onclick displays the form.

Was wondering if there is any efficient way to code instead of creating 4 different functions for 4 different forms? Below example is for 4 forms but I am working with multiple forms.

<div class="navbar">
  <div class="dropdown">
  <button class="dropbtn" onclick="myFunction1()">Category 1
    <i class="fa fa-caret-down"></i>
  </button>
  </div> 

//Same for other 3 categories

<div id="form1" style = "display:none">
<form action="#" method="post" id="demoForm1" class="demoForm1" >
    <fieldset>
        <legend>Use CTRL to select multiple options</legend>

        <p>
            <select name="demoSel[]" id="demoSel" size="4" multiple>
                <option value="ABC">ABC</option>
            </select>
            <input type="submit" value="Submit" />
            <textarea name="display" id="display" placeholder="view select list value(s) onchange" cols="20" rows="4" readonly></textarea>
        </p>

    </fieldset>
</form>
</div>


//Same for other 3 forms


  <script>

function myFunction1() {
document.getElementById("form1").style.display = '';
}

function myFunction2() {
  document.getElementById("form2").style.display = '';
}

function myFunction3() {
  document.getElementById("form3").style.display = '';
}

function myFunction4() {
  document.getElementById("form4").style.display = '';
}
</script>

Answer 1

It's generally not a good idea to use inline event handlers.

Next, add a data-* attribute to each button and remove the onclick attribute like:

<button class="dropbtn" data-target="form1">...</button>
<button class="dropbtn" data-target="form2">...</button>
<button class="dropbtn" data-target="form3">...</button>
<button class="dropbtn" data-target="form4">...</button>

Then, you can use .addEventListener() on these buttons with class dropbtn and update respective form element display property like:

const btns = document.querySelectorAll(".dropbtn");
btns.forEach(function(btn) {
  btn.addEventListener("click", function(cbox) {
     document.getElementById(this.dataset.target).style.display = '';
  });
});

Demo:

 const btns = document.querySelectorAll(".dropbtn"); btns.forEach(function(btn) { btn.addEventListener("click", function(cbox) { document.getElementById(this.dataset.target).style.display = ''; }); });

 <button class="dropbtn" data-target="form1">Form 1</button> <button class="dropbtn" data-target="form2">Form 2</button> <br><br> <form id="form1" style="display:none">Form 1 Content Here</form> <form id="form2" style="display:none">Form 2 Content Here</form>

Answer 2

Don't use on-event attributes:

<button onclick='eventHandler()'></button>

Use event listeners or on-event properties:

const btn = document.querySelector('button');

btn.addEventListener('click', eventHandler);

// OR

btn.onclick = eventHandler;

If you have multiple targets to click -- register the click event to a parent tag that all target tags share.

document.querySelector('main').onclick = toggleForm;

Instead of using .style on each <form> toggle classes

// CSS
.off { display: none }

// JavaScript
forms[idx].classList.toggle('off');

---

Demo

Note: Details are commented in demo

 /* - Reference the parent tag (<main>) - Register <main> to the click event - Event handler function toggleForm() is called on click */ document.querySelector('main').onclick = toggleForm; // Event handler always passes Event Object (event) function toggleForm(event) { // Collect all <form>s into a HTML Collection const forms = document.forms; // Collect all <button> into a NodeList const buttons = document.querySelectorAll('button'); // Reference the tag the user clicked (<button>) const clicked = event.target; // if a <button> was clicked... if (clicked.matches('button')) { //...toggle the <button>'s.on and.off classes clicked.classList.toggle('off'); clicked.classList.toggle('on'); /* - Convert buttons NodeList into a rel Array - Iterate through the buttons array and return the index of the clicked <button> */ let idx = [...buttons].flatMap((button, index) => clicked === button? [index]: []); /* - Toggle the.off class on the <form> located at the index that was obtained from the previous statement */ forms[idx].classList.toggle('off'); } }

 button { display: inline-block; width: 11ch } button.off::before { content: 'Show ' } button.on::before { content: 'Hide ' } form.off { display: none }

 <main> <button class='off' type='button'>A</button> <button class='off' type='button'>B</button> <button class='off' type='button'>C</button> <button class='off' type='button'>D</button> <hr> <form id='A' class='off'> <fieldset> <legend>Form A</legend> </fieldset> </form> <form id='B' class='off'> <fieldset> <legend>Form B</legend> </fieldset> </form> <form id='C' class='off'> <fieldset> <legend>Form C</legend> </fieldset> </form> <form id='D' class='off'> <fieldset> <legend>Form D</legend> </fieldset> </form> </main>