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问题:

I have two buttons and if I click on some button I need to change value in input text and change total price (product price * value of button - 2 or 4 Qty).

I know that it's simple but I'm not good in javascript or jQuery. Answer in jsfiddle would be best.
My jsfiddle is here http://jsfiddle.net/J7m7m/1/

My simple code:

Product price: $500
<br>
Total price: $500
<br>
<input type="button" onclick="change()" value="2&#x00A;Qty">
<input type="button" value="4&#x00A;Qty">
<br>
Total <input type="text" id="count" value="1">

回答1:

Another simple solution for this case using jQuery. Keep in mind it's not a good practice to use inline javascript.

JsFiddle

I've added IDs to html on the total price and on the buttons. Here is the jQuery.

$('#two').click(function(){
    $('#count').val('2');
    $('#total').text('Product price: $1000');
});

$('#four').click(function(){
    $('#count').val('4');
    $('#total').text('Product price: $2000');
});

回答2:

Try This(Simple javascript):-

<!DOCTYPE html>
<html>
   <script>
      function change(value){
      document.getElementById("count").value= 500*value;
      document.getElementById("totalValue").innerHTML= "Total price: $" + 500*value;
      }

   </script>
   <body>
      Product price: $500
      <br>
      <div id= "totalValue">Total price: $500 </div>
      <br>
      <input type="button" onclick="change(2)" value="2&#x00A;Qty">
      <input type="button" onclick="change(4)" value="4&#x00A;Qty">
      <br>
      Total <input type="text" id="count" value="1">
   </body>
</html>

Hope this will help you..

回答3:

using html5 data attribute...

try this

Html

Product price: $<span id="product_price">500</span>

<br>Total price: $500
<br>
<input type="button" data-quantity="2" value="2&#x00A;Qty">
<input type="button" data-quantity="4" class="mnozstvi_sleva" value="4&#x00A;Qty">
<br>Total
<input type="text" id="count" value="1">

$(function(){
$('input:button').click(function () {
  $('#count').val($(this).data('quantity') * $('#product_price').text());
});
});

fiddle here

回答4:

And here is the non jQuery answer.

Fiddle: http://jsfiddle.net/J7m7m/7/

function changeText(value) {
     document.getElementById('count').value = 500 * value;   
}

HTML slight modification:

Product price: $500
<br>
Total price: $500
<br>
<input type="button" onclick="changeText(2)" value="2&#x00A;Qty">
<input type="button" class="mnozstvi_sleva" value="4&#x00A;Qty" onClick="changeText(4)">
<br>
Total <input type="text" id="count" value="1"/>

EDIT: It is very clear that this is a non-desired way as pointed out below (I had it coming). So in essence, this is how you would do it in plain old javascript. Most people would suggest you to use jQuery (other answer has the jQuery version) for good reason.

回答5:

This will work fine for you

   <!DOCTYPE html>
    <html>
    <head>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

    <script>
    function myfun(){
    $(document).ready(function(){

        $("#select").click(
        function(){
        var data=$("#select").val();
            $("#disp").val(data);
                            });
    });
    }
    </script>
    </head>
    <body>
    <p>id <input type="text" name="user" id="disp"></p>
    <select id="select" onclick="myfun()">
    <option name="1"value="one">1</option>
    <option name="2"value="two">2</option>
    <option name="3"value="three"></option>
    </select>
    </body>
    </html>

回答6:

My Attempt ( JsFiddle)

Javascript

$(document).ready(function () {
    $('#buttons input[type=button]').on('click', function () {
        var qty = $(this).data('quantity');
        var price = $('#totalPrice').text(); 
        $('#count').val(price * qty);
    });
});

Html

  Product price:$500
<br>Total price: $<span id='totalPrice'>500</span>
<br>
<div id='buttons'>
    <input id='qty2' type="button" data-quantity='2' value="2&#x00A;Qty">
    <input id='qty2' type="button" class="mnozstvi_sleva" data-quantity='4' value="4&#x00A;Qty">
</div>
<br>Total
<input type="text" id="count" value="1">