先上代码：
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext('2d');
var r = canvas.width / 2;
var arr=["red","orange","blue","green"];
for(var i=0;i
ctx.beginPath();
ctx.arc(r, r, r, Math.PI * (i)/2,Math.PI * (i+1)/2);
ctx.fillStyle = arr[i];
ctx.fill();
}
function isInPath (x, y){
return ctx.isPointInPath(x, y)//判断是否在某个区域内
}
canvas.addEventListener('click', function(e){
for(var i=0;i
ctx.beginPath();
ctx.arc(r, r, r, Math.PI * (i)/2,Math.PI * (i+1)/2);
if(isInPath(e.offsetX, e.offsetY)) {
alert(arr[i])
}
}
})
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