如何在 JavaScript 中的一个函数中显示每个按钮

Question

So, I'm trying to build a calculator and the first thing I want to do is to display all the buttons in my output. I have created a function called displayButtons and inside, I got the first 2 buttons by id however, when I try to display them, only the number 2 displays. One way to fix this is to create a function for each numbers and then it'll work but that's not what I want. I've also tried nesting the functions for each number within a function, but I wasn't able to call it properly onclick. Any ideas? Thanks in advance!

HTML code:

<div id="output"></div>
        <div class="numbers">
            <button value="1" id="one" onclick="displayButtons()">1</button>
            <button value="2" id="two" onclick="displayButtons()">2</button>

JS code:

function displayButtons() {

    var one = document.getElementById("one").value;
    document.getElementById("output").innerHTML = one;


    var two = document.getElementById("two").value;
    document.getElementById("output").innerHTML = two

}

Answer 1

Have you tried a for loop? you'd be able to add a click functionality with a closure or 'let' keyword or a separate function.. run the following in codepen, see how it works and if this is something that can be useful.

    function createButtons() {
       //let is block scoped, not function scoped
        for (let i = 1; i <= 5; i++) {
          var body = document.getElementsByTagName("BODY")[0];
          var button = document.createElement("BUTTON");
          button.innerHTML = 'Button ' + i;
          button.onclick = function() {
               alert('This is button ' + i);
          }
          body.appendChild(button);
        }
     }
      
     createButtons();

Answer 2

There is multiple solutions for this, but here a simple one: you can use the event data to get the info of the button clicked, then you can do what you want with these values.

HTML

<div id="output"></div>
<div class="numbers">
  <button value="1" id="one">1</button>
  <button value="2" id="two">2</button>
</div>

JS

document.querySelectorAll('.numbers button').forEach(button => { 
  button.addEventListener('click', (e) => {
    console.log(e.target.id, e.target.value)
  })
})

Answer 3

To display the output on clicking of numbers, you can pass in a this object inside the function like this

<button value="1" id="one" onclick="displayButtons(this)">1</button>

and when you click on it, you'll receive the button node inside the function full code would be

   <div class="numbers">
        <button value="1" id="one" onclick="displayButtons(this)">1</button>
        <button value="2" id="two" onclick="displayButtons(this)">2</button>
    </div>


    <script>
        function displayButtons(button) {
            document.getElementById("output").innerHTML += button.value
        }
    </script>

Answer 4

You keep overwriting the innerHTML , to that's why you only see the 2.

I recommend that you change your approach. All of your buttons are in div.numbers . Add a single click event listener to the numbers div. This event listener will fire if any of the buttons are pressed, because the click event bubbles. This is called event delegation .

In the click event handler, you can see which button has been clicked and add the value of the clicked button to div#output .

 const output = document.querySelector('#output'); const numbers = document.querySelector('.numbers'); numbers.addEventListener('click', ({ target }) => { if (!target.hasAttribute('value')) { return; } output.textContent += target.value; });

 <div id="output"></div> <div class="numbers"> <button value="1">1</button> <button value="2">2</button> <button value="3">3</button> <button value="4">4</button> <button value="5">5</button> </div>

Answer 5

Each time you press a button, you're overwriting the entire innerHTML, so you're replacing the whole content by the new one.

You should append the value instead, using += operator

Furthermore you may consider to use innerText instead of innerHTML, and use addEventListener instead of onclick=

<div id="output"></div>
<div class="numbers">
    <button value="1" id="one">1</button>
    <button value="2" id="two">2</button>
</div>

... and after ...

<script>
document.querySelector(".numbers").addEventListener('click', e => {
    if( e.target.nodeName === "BUTTON" )
        document.getElementById("output").innerText += e.target.value;
});
</script>

Answer 6

You have to get the id of every button in onclick parameter like: onclick= displayButtons(id) it will create different click event for every buttton then

function displayButton(id){
let oldValue = document.getElementById("output").innerHtml
document.getElementById("output").innerHTML = oldValue + id;}