如何处理jQuery中的数字输入更改? [英] How do I handle number input changes in jQuery?

问题描述

我正在尝试使用jQuery和HTML创建一个结帐菜单，但我无法获得输入框，以使项目数量可预期地运行.当我使用光标更改输入值时，"price"变量的输出为"NaN".当我使用箭头键时，价格会更新一次，但在第一次更改后会失败.如何获取数字输入值，将其乘以<p>标记中的文本(价格)，并在每次数字增加或减少时更新文本?到目前为止，我已经拥有了这么多:

I'm trying to create a checkout menu with jQuery and HTML and I am having trouble getting the input box for the item quantity to behave predictably. When I use the cursor to change the input value, the output for the 'price' variable is "NaN". When I use the arrow keys, the price updates once, but fails after the first change. How do I get the number input value, multiply it by the text (the price) in the <p> tag, and update the text every time the number is increased or decreased? I've got this much so far on my own:

这是我的HTML:

<input id="quantity" size="30" type="number" value="1" />
<p id="total">29.99</p>

还有我的JS:

$(document).ready(function() {
  function updatePrice() {
  var num = parseInt($("#quantity").val());
  var price = (num) * parseFloat($("#total").text());
  var total = price.toFixed(2);
  $("#total").replaceWith(total);
}
$(document).on("change, keyup, input", "#quantity", updatePrice);
});

JS小提琴.

推荐答案

仅需进行一些更改即可使您的代码正常工作.请注意，您仍然需要处理负数(通过字段属性?)以及0.

There are only a few changes required to make your code work. Be aware that you still need to handle negative numbers (by field properties?) as well as 0.

$(document).ready(function() {
    // grep the price only once...
    var price = parseFloat($("#total").text());        
    function updatePrice() {        
        var sum, num = parseInt($(this).val(),10);
        // if we have a number
        if(num) {
          // update info text
          sum = num * price;
          $("#total").text(sum.toFixed(2));
        }
    }
    $(document).on("change, mouseup, keyup", "#quantity", updatePrice);
});

小提琴在这里.

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