输入框的值不增加还是减少？

Question

I have made 2 buttons one for increment and another for decrement but when I click on button + it does not increment value of the input box similarly it does not decrements the value from input box on clicking button - 我已经制作了2个按钮，一个用于增加，另一个用于减少，但是当我单击按钮+时，它不会类似地增加输入框的值，也不会在单击按钮时减少输入框的值-

main.js: main.js：

var currentvalue = document.getElementById("date").value;

console.log(currentvalue);


function increment () {
  var newvalue = parseInt(currentvalue) + 1;
  document.getElementById("date").value = newvalue;
}

function decrement () {
  var newvalue = parseInt(currentvalue) - 1;
  document.getElementById("date").value = newvalue;
}

index.html: index.html：

<body>

    <div id="center">
        <label for="name">Date</label>
        <p></p>
        <button type="button" class="btn btn-success" id="plus" onclick="increment()">+</button>
        <input type="text" id="date" value="1">
        <button type="button" class="btn btn-danger" id="minus" onclick="decrement()">-</button>

    </div>

<script type="text/javascript" src="main.js"></script>
<link rel="stylesheet" type="text/css" href="index.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
</body>

Screenshot: 屏幕截图：

Answer 1

Place this var currentvalue = document.getElementById("date").value; 放置此var currentvalue = document.getElementById("date").value; inside the function because outside function it will execute only once during load and then the value will be set in it 在函数内部，因为在加载期间它将仅执行一次外部函数，然后在其中设置值

 function increment() { var currentvalue = document.getElementById("date").value; var newvalue = parseInt(currentvalue) + 1; document.getElementById("date").value = newvalue; } function decrement() { var currentvalue = document.getElementById("date").value; var newvalue = parseInt(currentvalue) - 1; document.getElementById("date").value = newvalue; }

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <div id="center"> <label for="name">Date</label> <p></p> <button type="button" class="btn btn-success" id="plus" onclick="increment()">+</button> <input type="text" id="date" value="1"> <button type="button" class="btn btn-danger" id="minus" onclick="decrement()">-</button> </div>

输入框的值不增加还是减少？

问题描述

1 个解决方案

解决方案1
2 已采纳 2018-02-24 07:12:38

输入框的值不增加还是减少？

问题描述

1 个解决方案

解决方案1 2 已采纳 2018-02-24 07:12:38

解决方案1
2 已采纳 2018-02-24 07:12:38