如何在一个输入框中在javascript中创建附加功能

Question

我正在试图制作JavaScript计算器。我想在JavaScript中创建简单的加法函数，但不知道如何构建该逻辑，需要某人的帮助，并且在我的代码中有一个输入文本字段。

代码包含输入按钮，这是数字现在我需要帮助。那么我如何在JavaScript中添加函数呢？

function plus() 
 
    { 
 
     var textInputval=0; 
 
     var textInputval1=2; 
 
     var temp=0; 
 
     textInputval = parseInt(document.getElementById('new').value); 
 
     textInputval1 = parseInt(document.getElementById('new').value); 
 
     temp = textInputval + textInputval1; 
 
     console.log(textInputval); 
 
     console.log(textInputval1); 
 
    }

<div id = "cal-container"> 
 
    <form name="calculator"> 
 
     <input type="text" name="answer" value="" id="new"> 
 
     <br> 
 
     <input type="button" value=" 1 " onclick="one()" /> 
 
     <input type="button" value=" 2 " onclick="two()" /> 
 
     <input type="button" value=" 3 " onclick="three()" /> 
 
     <input type="button" value=" + " onclick="plus()" /> 
 
    </form> 
 
</div>

Answer 1

function action(method) { 
 
      var a = parseInt(document.getElementById("num1").value); 
 
      var b = parseInt(document.getElementById("num2").value); 
 
      var result = null; 
 

 
      switch (method) { 
 
      case 'add': 
 
       result = a + b; 
 

 
       break; 
 
      case 'subtract': 
 
       result = a - b; 
 
       break; 
 
      case 'multiply': 
 
       result = a * b; 
 
       break; 
 
      case 'divide': 
 
       if (b != 0) { 
 
       result = a/b; 
 
       } else { 
 
       alert('Can\'t divide by 0'); 
 

 
       return; 
 
       } 
 

 
       break; 
 
      } 
 

 
      if (result !== null) { 
 

 
      document.getElementById("result").value = result; 
 
      } else { 
 

 
      document.getElementById("num1").value = ""; 
 
      document.getElementById("num2").value = ""; 
 
      document.getElementById("result").value = ""; 
 
      } 
 
     }

<span style="margin-right:1px">Number 1 </span> 
 
<input id="num1" type="number"></br> 
 
<span style="margin-right:5px">Number 2</span><input id="num2" type="number"></br> 
 
<span style="margin-right:29px">Result</span><input id="result" type="number"> </br> 
 

 

 
<button id="add" onclick="action('add')">+</button> 
 
<button id="subtract" onclick="action('subtract')">-</button> 
 
<button id="multiply" onclick="action('multiply')">*</button> 
 
<button id="divide" onclick="action('divide')">/</button> 
 
<button id="clear" onclick="action('clear')">clear</button>