<!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>
<style>
html,
body {
margin: 0;
padding: 0;
}
main {
display: flex;
align-items: center;
justify-content: center;
height: 100vh;
background-color: #e0e3ed;
}
canvas {
border-radius: 0;
box-shadow: 0 0 18px rgba(0, 0, 0, 0.2);
}
</style>
</head>
<body onload="draw()">
<main>
<canvas width="600" height="300" id="bar-chart"></canvas>
</main>
<script type="text/javascript">
const months = ["一月", '二月', "三月", '四月', '五月', '六月', "七月", '八月', '九月', "十一月", '十二月'];
function draw() {
var canvas = document.getElementById("bar-chart");
var ctx = canvas.getContext("2d");
// 获取canvas宽和高
let cWidth = canvas.width;
let cHeight = canvas.height;
ctx.fillStyle = "#f8fcff";
ctx.fillRect(0, 0, cWidth, cHeight);
// 计算9个柱子的位置
// canvas 内边距
let padding = 40;
// 柱子的高度
let width = 8;
// 柱子最大高度
let maxHeight = (cHeight - padding * 2) / 2;
// 柱子最小高度
let minHeight = maxHeight / 2;
// 柱子间距
let barGap = (cWidth - 2 * padding - 9 * width) / 8;
// 柱子圆角
let radius = 5;
// y坐标起始于canvas中间
let y = cHeight / 2;
for (let i = 0; i < 9; i++) {
// 柱子上半部分高度，随机产生[minHeight,maxHeight]区间的数字
let height1 = Math.floor(Math.random() * (maxHeight - minHeight + 1) + minHeight);
// 同样的下半部分高度
let height2 = Math.floor(Math.random() * (maxHeight - minHeight + 1) + minHeight);
// 计算每个柱子起始x坐标的位置
let x = padding + (barGap + width) * i;
// 画柱状图
drawBar(ctx, x, y, width, height1, height2, radius);
// 画月份
ctx.fillStyle = "#747d8c";
ctx.textAlign = "center";
// 设置文字粗细
ctx.font = "300 12px sans-serif";
// 在柱子中间画文字
ctx.fillText(months[i], x + width / 2, y + maxHeight + 20)
}
}
function drawBar(ctx, x, y, width, height1, height2, radius) {
ctx.beginPath();
// 画上半部分，四条边，两个角
ctx.moveTo(x, y);
ctx.lineTo(x, y - height1 + radius);
ctx.arcTo(x, y - height1, x + radius, y - height1, radius);
ctx.lineTo(x + width - radius, y - height1);
ctx.arcTo(x + width, y - height1, x + width, y - height1 + radius, radius);
ctx.lineTo(x + width, y);
ctx.lineTo(x, y);
ctx.fillStyle = "#341F97";
ctx.fill();
// 下半部分
ctx.beginPath();
ctx.moveTo(x, y);
ctx.lineTo(x, y + height2 - radius);
ctx.arcTo(x, y + height2, x + radius, y + height2, radius);
ctx.lineTo(x + width - radius, y + height2);
ctx.arcTo(x + width, y + height2, x + width, y + height2 - radius, radius);
ctx.lineTo(x + width, y);
ctx.lineTo(x, y);
ctx.fillStyle = "#54A0FF";
ctx.fill();
// ctx.stroke();
}
</script>
</body>
</html>
效果图：
