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How to find the area of ​​a circle using js

醉折花枝作酒筹
醉折花枝作酒筹Original
2021-04-08 18:43:008679browse

Method to calculate the circle area: 1. Create an input tag and receive the radius value; 2. Use "document.getElementById('id').value" to get the radius value in the input input box; 3. , use the area formula "area=3.14*(radius*radius)" to find the area of ​​the circle.

How to find the area of ​​a circle using js

The operating environment of this tutorial: Windows 7 system, JavaScript version 1.8.5, Dell G3 computer.

The specific condition is to enter a radius, then find the area, round to 2 decimal places,

<!DOCTYPE html>
<html lang="en"><head>
<meta charset="UTF-8">
<title>Document</title>
</head>
    <body>
    输入圆的半径:<input type="text" id="inp">
    <input type="button" value="确定" onclick="test()"> 
  </body>
  </html>
  <script>
    function test(){
        var inp = parseFloat(document.getElementById(&#39;inp&#39;).value);        
        var s = 3.14 * (inp * inp);
        alert(&#39;面积为:&#39; + s)
    }
    </script>

[Recommended learning: javascript video tutorial]

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