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javascript - 使用 Javascript 的计算器

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主内容类，其下有一个 ID 为 的文本框displaytext。此外，有 3 行，每行包含数字，然后是另一行包含符号。我附上了下面的代码以供参考。

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>

这里的问题是，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。

标签： javascripthtmlcssfrontend

解决方案

buttons 是表单元素，它们的默认type值为submit，为按钮添加type="button"属性，因此它们不会发送表单。

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

HTML<button>元素表示一个可单击的按钮，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>

您还可以同时处理循环上的点击功能和属性类型

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>

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