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When I click numbers, I always get the same result. Why? Here is my HTML code:

<!DOCTYPE html>
<html>
   <body>
      <p id="demo"></p>
      <input type="button" id="myBtn" onclick="myFunction()" value="1">
      <input type="button" id="myBtn" onclick="myFunction()" value="2">
      <input type="button" id="myBtn" onclick="myFunction()" value="3">
      <input type="button" id="myBtn" onclick="myFunction()" value="4">
      <input type="button" id="myBtn" onclick="myFunction()" value="5">
      <input type="button" id="myBtn" onclick="myFunction()" value="6">
      <input type="button" id="myBtn" onclick="myFunction()" value="7">
      <input type="button" id="myBtn" onclick="myFunction()" value="8">
      <input type="button" id="myBtn" onclick="myFunction()" value="9">
      <input type="button" id="myBtn" onclick="myFunction()" value="0">
      <script>
         function myFunction() {
             var x = document.getElementById("myBtn").value;
             document.getElementById("demo").innerHTML = x;
         }
      </script>
   </body>
</html>

When I click numbers, I always get the same result. Why? Here is my HTML code:

<!DOCTYPE html>
<html>
   <body>
      <p id="demo"></p>
      <input type="button" id="myBtn" onclick="myFunction()" value="1">
      <input type="button" id="myBtn" onclick="myFunction()" value="2">
      <input type="button" id="myBtn" onclick="myFunction()" value="3">
      <input type="button" id="myBtn" onclick="myFunction()" value="4">
      <input type="button" id="myBtn" onclick="myFunction()" value="5">
      <input type="button" id="myBtn" onclick="myFunction()" value="6">
      <input type="button" id="myBtn" onclick="myFunction()" value="7">
      <input type="button" id="myBtn" onclick="myFunction()" value="8">
      <input type="button" id="myBtn" onclick="myFunction()" value="9">
      <input type="button" id="myBtn" onclick="myFunction()" value="0">
      <script>
         function myFunction() {
             var x = document.getElementById("myBtn").value;
             document.getElementById("demo").innerHTML = x;
         }
      </script>
   </body>
</html>

  • javascript
  • html
Share Improve this question edited May 28, 2017 at 22:16 Badacadabra 8,5177 gold badges31 silver badges54 bronze badges asked Jun 21, 2015 at 7:38 Nurul Akter TowhidNurul Akter Towhid 3,2462 gold badges35 silver badges36 bronze badges
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3 Answers 3

Reset to default 2

1) Ids must be unique. Rewrite your HTML to use classes or unique ids.

2) To get value in myFunction you can simply pass this from elenment to access to clicked button.

<input type="button" id="myBtn" onclick="myFunction(this)" value="1">

....

function myFunction(button) {
    var x = button.value;
    document.getElementById("demo").innerHTML = x;
}

http://jsfiddle/0sewtjLs/

Still have the problem in case of more than 1digit number

Just concat string:

document.getElementById("demo").innerHTML += x;

http://jsfiddle/0sewtjLs/1/

try

<input type="button" id="myBtn" onclick="myFunction(1)" >
<input type="button" id="myBtn" onclick="myFunction(2)" >
<input type="button" id="myBtn" onclick="myFunction(3)" >
<input type="button" id="myBtn" onclick="myFunction(4)" >
<input type="button" id="myBtn" onclick="myFunction(5)" >
<input type="button" id="myBtn" onclick="myFunction(6)" >
<input type="button" id="myBtn" onclick="myFunction(7)" >
<input type="button" id="myBtn" onclick="myFunction(8)" >
<input type="button" id="myBtn" onclick="myFunction(9)" >
<input type="button" id="myBtn" onclick="myFunction(0)" >

<script>
function myFunction(x) {
    document.getElementById("demo").innerHTML = x;
}
</script>

you can also keep logic only in Javascript, and removing the "onclick" on HTML. In the code bellow, all your buttons have "myBtn" class. You can have infinite time the same class. But ID's are unique, be carefull.

In this code I get the all class "myBtn", wich return an Array. On this array, I making a loop and add an eventListner listening clicks and calling the myFunction function.

 <p id="demo"></p>

 <input type="button" class="myBtn" value="1">
 <input type="button" class="myBtn" value="2">
 <input type="button" class="myBtn" value="3">
 <input type="button" class="myBtn" value="4">
 <input type="button" class="myBtn" value="5">
 <input type="button" class="myBtn" value="6">
 <input type="button" class="myBtn" value="7">
 <input type="button" class="myBtn" value="8">
 <input type="button" class="myBtn" value="9">
 <input type="button" class="myBtn" value="0">

<script>

 const allBtns = document.querySelectorAll('.myBtn');
 allBtns.forEach( element => {
   element.addEventListener('click', myFunction);
 })

 function myFunction(e) {
   const value = e.target.value;
   document.getElementById("demo").innerHTML = value;
 }
</script>

本文标签： javascriptHow to display number input using button for calculator in HTMLStack Overflow

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