我想使用 javascript 创建一个符号。它需要创建圆形和矩形。我创建了圆形和矩形。但是当矩形放在圆形下面时，则圆形不显示。如何解决这个问题？
var circle = document.getElementById('canvas1');
var ctx = circle.getContext('2d');
ctx.beginPath();
ctx.arc(300, 300, 50, 0, 2 * Math.PI);
ctx.stroke();
//create gradient
var grd = ctx.createRadialGradient(300, 300, 50, 300, 300, 5);
var fillColor = 'black';
ctx.fillStyle = fillColor;
ctx.fill();
var rect = document.getElementById('canvas2');
var ctx2 = rect.getContext('2d');
ctx2.beginPath();
ctx2.rect(200, 10, 200, 40);
ctx2.stroke();
var grd2 = ctx2.createLinearGradient(0, 0, 100, 100);
grd2.addColorStop(0, "black");
grd2.addColorStop(1, "white");
ctx2.fillStyle = grd2;
ctx2.fill();<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<canvas id="canvas1" width="800" height="250"></canvas>
<canvas id="canvas2" width="800" height="300"></canvas>
<script src="index.js"></script>
</body>
</html>代码中唯一的问题是画布高度为 250 像素，并且您在画布外 (300,300) 处绘制圆圈
我刚刚改变
arcctx.arc(100, 100, 50, 0, 2 * Math.PI);
var circle = document.getElementById('canvas1');
var ctx = circle.getContext('2d');
ctx.beginPath();
ctx.arc(100, 100, 50, 0, 2 * Math.PI); // changed this line
ctx.stroke();
//create gradient
var grd = ctx.createRadialGradient(300, 300, 50, 300, 300, 5);
var fillColor = 'black';
ctx.fillStyle = fillColor;
ctx.fill();
var rect = document.getElementById('canvas2');
var ctx2 = rect.getContext('2d');
ctx2.beginPath();
ctx2.rect(200, 10, 200, 40);
ctx2.stroke();
var grd2 = ctx2.createLinearGradient(0, 0, 100, 100);
grd2.addColorStop(0, "black");
grd2.addColorStop(1, "white");
ctx2.fillStyle = grd2;
ctx2.fill();<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<canvas id="canvas1" width="800" height="250"></canvas>
<canvas id="canvas2" width="800" height="300"></canvas>
<script src="index.js"></script>
</body>
</html>