我必须使用香草JS在画布上制作一个条形图，没有Charts.js或jquery。条形对于画布大小而言太长，因此无法显示条形的完整长度。如何缩放标尺，使其适合硬编码的画布高度？
提前感谢！
<!DOCTYPE html>
<html lang="en" dir="ltr">
<head>
<meta charset="utf-8">
<title>chart</title>
</head>
<body>
<br>
<br>
<canvas id="canvas" width="400" height="400"></canvas>
<style> canvas {
border: 1px solid black;
}
</style>
<script>
window.onload = function canvas() {
let canvas = document.getElementById('canvas');
let ctx = canvas.getContext('2d');
let data = [['A', 439], ['B', 228.23], ['C', 2580.39], ['D', 279]];
let barwidth = 50;
let ygap = 30;
let bargap = 100;
let x = 50;
y = canvas.height - ygap;
canvas.width = data.length * (bargap) + x;
ctx.moveTo(x - 5, y);
ctx.lineTo(canvas.width, y); // Base line of graph
ctx.stroke();
for (let i = 0; i < data.length; i++) {
ctx.textAlign = 'left';
ctx.textBaseline = 'top';
ctx.fillStyle = 'black';
ctx.fillText(data[i][0], x, y + 5); // Write base text for classes
ctx.beginPath();
ctx.lineWidth = 2;
y1 = y - data[i][1]; // Coordinate for top of the Bar
x1 = x;
ctx.fillStyle = 'black';
ctx.fillText(data[i][1], x1, y1 - 20); // text at top of the bar
ctx.fillStyle = 'black'; // fill Colur of bar
ctx.fillRect(x1, y1, barwidth, data[i][1]);// Filled bar
x += bargap
}
}
</script>
</body>
</html>
这是获取height的canvas的方法：
document.getElementById（'canvas'）。height
因此，这将是最低点的坐标。画布顶部的坐标为0。此function计算给定百分比的坐标：
function percent(input, canvasHeight) {
return canvasHeight - (canvasHeight * input / 100);
}