Enter two numbers in html to realize addition, subtraction, multiplication and division functions

1. parseFloat() function Make a simple calculator on a web page, enter two numbers in the text box, and be able to add, subtract, multiply and divide the two numbers. The parseFloat() function parses a string and returns a floating point number. This function specifies whether the first character in a string is a number. If it is, the string is parsed until the end of the number is reached and the number is returned as a number. instead of as a string. Syntax: parseFloat(string); 2. JavaScript global properties

1. parseFloat() function

Make a simple calculator on a web page, enter two numbers in the text box, and be able to add, subtract, multiply and divide the two numbers.
The parseFloat() function parses a string and returns a floating point number.
This function specifies whether the first character in a string is a number. If it is, the string is parsed until the end of the number is reached and the number is returned as a number.
instead of as a string.
Syntax: parseFloat(string);

2. JavaScript global properties

property	describe
Infinity	A value representing positive infinity.
NaN	Indicates whether a value is a numeric value.
undefined	Indicates an undefined value.

3. Complete code

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script type="text/javascript">
       function cal(){
           var nums = document.getElementsByName("num");
           var sz = document.getElementsByName("js");
           var result = document.getElementsByName("rs");
           var n1 = parseFloat(nums[0].value);
           var n2 = parseFloat(nums[1].value);
           /*parseFloat() function parses a string and returns a floating point number.
           This function specifies whether the first character in a string is a number. If it is, the string is parsed until the end of the number is reached and the number is returned as a number.
           instead of as a string.
        */
            switch(sz[0].value){
            case "add" : 
            result[0].value = n1 + n2;
            break;
            case "min" : 
            result[0].value = n1 - n2;
            break;
            case "mul" : 
            result[0].value = n1 * n2;
            break;
            case "div" : 
            result[0].value = n1/n2; 
            break;
              }
          }
      </script>
</head>
<body>
    <div align="center">
        <input type="text" name="num" value="" onkeyup="value=value.replace(/^\D*(\d*(?:\.\d{0,2})?).*$/g, '$1')" />
        <select name="js" size="1">
            <option value="add">+</option>
            <option value="min">-</option>
            <option value="mul">*</option>
            <option value="div">/</option>
        </select>
   <input type="text" name="num" value=""onkeyup="value=value.replace(/^\D*(\d*(?:\.\d{0,2})?).*$/g, '$1')" />
  =
   <input type="text" name="rs" value=""/><br>
   <button id="btn"onclick="cal()">Calculate</button>
</div>
</body>
</html>

Effect display:

insert image description here

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Enter two numbers in html to realize addition, subtraction, multiplication and division functions

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