我尝试解决这个问题，但似乎找不到解决方案。经过几个小时的摆弄，我发现问题出在按钮标签或 onclick 属性中(如果我错了，请纠正我)。
我的目标是通过按钮让白点移动
<!DOCTYPE html>
<html>
<head>
<title></title>
<script type="text/javascript">
window.onload = function()
{
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 345;
canvas.height = 410;
canvas.style.border = "1px solid white";
var left = document.getElementById("left");
left.onclick = "playerLeft()";
var x = Math.round(canvas.width/2);
var y = Math.round(canvas.width/2);
var rectWidth = 5, rectHeight = 5;
var fps = 30, frames = 1000/fps;
var colour = "white";
var trailColour = "blue";
ctx.fillStyle = colour;
ctx.fillRect(x,y,rectWidth,rectHeight);
function playerLeft() {
ctx.fillStyle = trailColour;
ctx.fillRect(x,y,rectWidth,rectHeight);
x -= 6;
ctx.fillStyle = colour;;
ctx.fillRect(x,y,rectWidth,rectHeight);
}
function playerRight() {
ctx.fillStyle = trailColour;
ctx.fillRect(x,y,rectWidth,rectHeight);
x += 6;
ctx.fillStyle = colour;
ctx.fillRect(x,y,rectWidth,rectHeight);
}
function playerUp() {
ctx.fillStyle = trailColour;
ctx.fillRect(x,y,rectWidth,rectHeight);
y -= 6;
ctx.fillStyle = colour;
ctx.fillRect(x,y,rectWidth,rectHeight);
}
function playerDown() {
ctx.fillStyle = trailColour;
ctx.fillRect(x,y,rectWidth,rectHeight);
y += 6;
ctx.fillStyle = colour;
ctx.fillRect(x,y,rectWidth,rectHeight);
}
}
</script>
</head>
<body style="background-color: black">
<canvas id="canvas"></canvas>
<div style="text-align: center; padding: 5px">
<button id="left">Left</button>
<button id="up">Up</button>
<button id="down">Down</button>
<button id="right">Right</button>
</div>
</body>
</html>
最佳答案
不使用 onxyz="..." 样式事件处理程序的众多原因之一是，从它们调用的任何函数都必须是全局。您的函数不是，它们是 window.onload 回调的本地函数。
相反，直接分配函数引用，这有点老式:
left.onclick = playerLeft;
或者使用允许多个处理程序的更现代的技术:
left.addEventListener("click", playerLeft);
关于javascript - 属性 onclick ="function()"未按预期运行？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42514383/