使用 Javascript 的计算器答案

【问题标题】：Calculator using Javascript使用 Javascript 的计算器
【发布时间】：2020-11-15 13:11:34
【问题描述】：

我正在尝试使用 Vanilla Javascript 制作一个简单的计算器。有一个div，其类为main-content，其下有一个ID 为displaytext 的文本框。此外，有 3 行，每行包含数字，然后是另一行包含符号。我已附上以下代码以供参考。

const displayText = document.getElementById("displaytext"); // storing the ID of the textbox in a variable
const seven = document.getElementById("seven");

seven.addEventListener('click',function () {
    displayText.value+=seven.value;
})

@import url('https://fonts.googleapis.com/css2?family=Roboto&display=swap');
@import url('https://fonts.googleapis.com/css2?family=Open+Sans&display=swap');


*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* .main-content{
    display: flex;
    justify-content: center;
    align-items: center;
} */

.heading{
    margin: 20px;
    padding:15px;
}

.heading h2{
    text-align: center;
    font-family: 'Open Sans', sans-serif;
    font-size: 45px;
    font-weight: 800;
    margin-left: -20px;
}

.main-content{
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 75vh;
    background-color: rgb(255, 49, 49,0.5);
    width: 30%;
    margin: 0px 520px;
    border: 3px solid rgb(197, 95, 0);
    border-radius: 30px;
}

.row1,.row2,.row3,.row4{
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
    /* margin: 10px; */
    padding: 10px;
    margin-left: -70px;
}

.element{
    padding:25px;
    background-color: white;
    text-align: center;
    margin: 7.5px;
    
    font-size: 25px;
    font-family: 'Roboto', sans-serif;
    border: 4px solid rgb(102, 102, 102);
    border-radius: 15px;
    cursor: pointer;
    width: 50%;

}

.symbol{
    display: flex;
    flex-direction: column;
    /* align-items: flex-end; */
    /* justify-content: right; */
    margin-top: -355px;
    margin-left: 300px;
}

.symbol-element{
    padding: 17.5px;
    margin: 10px 0px;
    border: 4px solid rgb(102, 102, 102);
    font-size: 25px;
    font-family: 'Roboto', sans-serif;
    border-radius: 15px;
    cursor: pointer;
    width: 120%;
    text-align: center;
    height: 66px;
    /* transition: 0.5s ease-in-out; */
}

.displaytext{
    border-radius: 10px;
    /* margin-left: 5px; */
    height: 100px;
    width: 75%;
    padding: 20px;
    /* margin: 20px 0px; */
    margin-left: 35px;
    margin-top: 20px;
    border: none;
    font-size: 17px;
    /* transition: 5s ease-in-out; */
}

.element,.symbol-element,.displaytext:focus{
    outline: none;
}

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Calculator</title>

    <link rel="stylesheet" href="/calculator/style.css">
</head>

<body>

    <!-- main-container starts here -->

    <div class="main-container">

        <div class="heading">

            <h2>Calculator</h2>

        </div>

        <form class="main-content">

            <input type="text" class="displaytext" name="displaytext" id="displaytext">

            <div class="row1">
                <button class="element" value="7" id="seven">7</button>
                <button class="element" value="8">8</button>
                <button class="element" value="9">9</button>

            </div>

            <div class="row2">
                <button class="element" value="1">1</button>
                <button class="element" value="2">2</button>
                <button class="element" value="3">3</button>

            </div>

            <div class="row3">
                <button class="element" value="4">4</button>
                <button class="element" value="5">5</button>
                <button class="element" value="6">6</button>

            </div>

            <div class="symbol">
                <button class="symbol-element" value="+">+</button>
                <button class="symbol-element" value="-">-</button>
                <button class="symbol-element" value="*">*</button>
                <button class="symbol-element" value="/">/</button>

            </div>

           

               


            <!-- main-content ends here -->




    </div>

    <!-- outer div ends here -->

    <script src="/calculator/script.js"></script>

</body>

</html>

这里的事情是，每当我运行命令displayText.value+=seven.value; 时，该值会出现在文本框中只是一瞬间。我该如何解决。

【问题讨论】：

标签： javascript html css frontend

【解决方案1】：

buttons 是表单元素，它们的默认 type 是 submit ，给按钮添加 type="button" 属性，所以它们不会发送表单。

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/button

HTML <button> 元素代表一个可点击的按钮，用于提交表单或文档中的任何位置，以实现可访问的标准按钮功能。默认情况下，HTML 按钮以类似于用户代理运行平台的样式呈现，但您可以使用 CSS 更改按钮的外观。

const displayText = document.getElementById("displaytext"); // storing the ID of the textbox in a variable
const seven = document.getElementById("seven");

seven.addEventListener('click',function () {
    displayText.value+=seven.value;
})

@import url('https://fonts.googleapis.com/css2?family=Roboto&display=swap');
@import url('https://fonts.googleapis.com/css2?family=Open+Sans&display=swap');


*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* .main-content{
    display: flex;
    justify-content: center;
    align-items: center;
} */

.heading{
    margin: 20px;
    padding:15px;
}

.heading h2{
    text-align: center;
    font-family: 'Open Sans', sans-serif;
    font-size: 45px;
    font-weight: 800;
    margin-left: -20px;
}

.main-content{
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 75vh;
    background-color: rgb(255, 49, 49,0.5);
    width: 30%;
    margin: 0px 520px;
    border: 3px solid rgb(197, 95, 0);
    border-radius: 30px;
}

.row1,.row2,.row3,.row4{
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
    /* margin: 10px; */
    padding: 10px;
    margin-left: -70px;
}

.element{
    padding:25px;
    background-color: white;
    text-align: center;
    margin: 7.5px;
    
    font-size: 25px;
    font-family: 'Roboto', sans-serif;
    border: 4px solid rgb(102, 102, 102);
    border-radius: 15px;
    cursor: pointer;
    width: 50%;

}

.symbol{
    display: flex;
    flex-direction: column;
    /* align-items: flex-end; */
    /* justify-content: right; */
    margin-top: -355px;
    margin-left: 300px;
}

.symbol-element{
    padding: 17.5px;
    margin: 10px 0px;
    border: 4px solid rgb(102, 102, 102);
    font-size: 25px;
    font-family: 'Roboto', sans-serif;
    border-radius: 15px;
    cursor: pointer;
    width: 120%;
    text-align: center;
    height: 66px;
    /* transition: 0.5s ease-in-out; */
}

.displaytext{
    border-radius: 10px;
    /* margin-left: 5px; */
    height: 100px;
    width: 75%;
    padding: 20px;
    /* margin: 20px 0px; */
    margin-left: 35px;
    margin-top: 20px;
    border: none;
    font-size: 17px;
    /* transition: 5s ease-in-out; */
}

.element,.symbol-element,.displaytext:focus{
    outline: none;
}

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Calculator</title>

    <link rel="stylesheet" href="/calculator/style.css">
</head>

<body>

    <!-- main-container starts here -->

    <div class="main-container">

        <div class="heading">

            <h2>Calculator</h2>

        </div>

        <form class="main-content">

            <input type="text" class="displaytext" name="displaytext" id="displaytext">

            <div class="row1">
                <button class="element" value="7" id="seven" type="button">7</button>
                <button class="element" value="8">8</button>
                <button class="element" value="9">9</button>

            </div>

            <div class="row2">
                <button class="element" value="1">1</button>
                <button class="element" value="2">2</button>
                <button class="element" value="3">3</button>

            </div>

            <div class="row3">
                <button class="element" value="4">4</button>
                <button class="element" value="5">5</button>
                <button class="element" value="6">6</button>

            </div>

            <div class="symbol">
                <button class="symbol-element" value="+">+</button>
                <button class="symbol-element" value="-">-</button>
                <button class="symbol-element" value="*">*</button>
                <button class="symbol-element" value="/">/</button>

            </div>

           

               


            <!-- main-content ends here -->




    </div>

    <!-- outer div ends here -->

    <script src="/calculator/script.js"></script>

</body>

</html>

你也可以同时处理循环上的点击函数和属性类型

let displayText = document.getElementById("displaytext"); // storing the ID of the textbox in a variable
let btn = document.querySelectorAll(".element, .symbol-element"); // find all our calculator buttons
for (let i = 0; i < btn.length; i++) {// loop through btn found 
  btn[i].setAttribute("type", "button"); // remove the submit behavior 
  btn[i].addEventListener("click", function() {
    displayText.value += this.value; // add to display text the button value
  });
}

@import url('https://fonts.googleapis.com/css2?family=Roboto&display=swap');
@import url('https://fonts.googleapis.com/css2?family=Open+Sans&display=swap');
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

.heading {
  margin: 20px;
  padding: 15px;
}

.heading h2 {
  text-align: center;
  font-family: 'Open Sans', sans-serif;
  font-size: 45px;
  font-weight: 800;
  margin-left: -20px;
}

.main-content {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 75vh;
  background-color: rgb(255, 49, 49, 0.5);
  width: 30%;
  margin: 0px 520px;
  border: 3px solid rgb(197, 95, 0);
  border-radius: 30px;
}

.row1,
.row2,
.row3,
.row4 {
  display: flex;
  flex-direction: row;
  justify-content: center;
  align-items: center;
  /* margin: 10px; */
  padding: 10px;
  margin-left: -70px;
}

.element {
  padding: 25px;
  background-color: white;
  text-align: center;
  margin: 7.5px;
  font-size: 25px;
  font-family: 'Roboto', sans-serif;
  border: 4px solid rgb(102, 102, 102);
  border-radius: 15px;
  cursor: pointer;
  width: 50%;
}

.symbol {
  display: flex;
  flex-direction: column;
  /* align-items: flex-end; */
  /* justify-content: right; */
  margin-top: -355px;
  margin-left: 300px;
}

.symbol-element {
  padding: 17.5px;
  margin: 10px 0px;
  border: 4px solid rgb(102, 102, 102);
  font-size: 25px;
  font-family: 'Roboto', sans-serif;
  border-radius: 15px;
  cursor: pointer;
  width: 120%;
  text-align: center;
  height: 66px;
  /* transition: 0.5s ease-in-out; */
}

.displaytext {
  border-radius: 10px;
  /* margin-left: 5px; */
  height: 100px;
  width: 75%;
  padding: 20px;
  /* margin: 20px 0px; */
  margin-left: 35px;
  margin-top: 20px;
  border: none;
  font-size: 17px;
  /* transition: 5s ease-in-out; */
}

.element,
.symbol-element,
.displaytext:focus {
  outline: none;
}

<!-- main-container starts here -->

<div class="main-container">
  <div class="heading">
    <h2>Calculator</h2>
  </div>
  <form class="main-content">
    <input type="text" class="displaytext" name="displaytext" id="displaytext">
    <div class="row1">
      <button class="element" value="7">7</button>
      <button class="element" value="8">8</button>
      <button class="element" value="9">9</button>
    </div>

    <div class="row2">
      <button class="element" value="1">1</button>
      <button class="element" value="2">2</button>
      <button class="element" value="3">3</button>
    </div>

    <div class="row3">
      <button class="element" value="4">4</button>
      <button class="element" value="5">5</button>
      <button class="element" value="6">6</button>
    </div>

    <div class="symbol">
      <button class="symbol-element" value="+">+</button>
      <button class="symbol-element" value="-">-</button>
      <button class="symbol-element" value="*">*</button>
      <button class="symbol-element" value="/">/</button>
    </div>

    <!-- main-content ends here -->
  </form>

  <!-- outer div ends here -->
</div>

【讨论】：

【解决方案2】：

不要使用事件监听器，因为当你点击它时它会被调用或者您可以提及您的显示应该如何表示的时间。

【讨论】：

感谢您的贡献。您的回复更适合评论而不是答案。您可以在此处阅读有关回答指南的更多信息stackoverflow.com/help/how-to-answer
但我使用的是addEventListener，它似乎工作正常。完全没有问题。您能否再详细说明一下您的陈述？

【解决方案3】：

您似乎试图覆盖 const 变量（显示文本）。您可以使用 var 或 let，它应该可以正常工作。

如果你有兴趣构建一个计算器，我很快就会在这里：https://repl.it/@bryku/calculator

它有一些删除非数字、处理点击按钮和直接在文本框中输入的示例。也许您可以将其用作一些基础知识的参考。

【讨论】：