In JavaScript, the code to find the area of a circle is "Math.PI * Math.pow (radius, 2)"; "Math.PI" is used to obtain the value of pi "π", the pow of the Math object The () method is used to obtain the square value of the radius. Multiply the two obtained numbers to obtain the area of the circle.
The operating environment of this tutorial: Windows 10 system, JavaScript version 1.8.5, Dell G3 computer.
What is the code for finding the area of a circle in JavaScript
In JavaScript, you can use the Math object to implement mathematical operations. The Math object is used to perform mathematics. Task.
Math object is not a class of objects like Date and String, so there is no constructor Math().
For example:
var x = Math.PI; // 返回PI var y = Math.sqrt(16); // 返回16的平方根
There is also the pow() method
The syntax is:
Math.pow(x,y)
The pow() method returns x raised to the y power.
Let’s take a look at how to calculate the primary color area and perimeter based on an example. The example is as follows:
<!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>
</head>
<body>
<script>
//四舍五入
function round(number, X) {
X = (!X ? 2 : X);
return Math.round(number*Math.pow(10,X))/Math.pow(10,X);
}
var r = Number(prompt('请输入圆的半径'));
if(!isNaN(r)) {
var m = round(Math.PI * Math.pow(r, 2), 2);
alert('面积='+m);
} else {
alert('请输入数字!');
}
</script>
</body>
</html>Output result:
[Recommended learning: javascript advanced tutorial]
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