html5中监听canvas内部元素点击事件的三种方法

//计算两点距离
const getDistence = function (p1, p2) {
  return Math.sqrt((p1.x - p2.x)  (p1.x - p2.x) + (p1.y - p2.y)  (p1.y - p2.y))
};
//角度法判断点在多边形内部
const checkPointInPolyline = (point, polylinePoints) => {
    let totalA = 0;
    const A = point;
    for (let i = 0; i < polylinePoints.length; i++) {
        let B, C;
        if (i === polylinePoints.length - 1) {
            B = {
                x: polylinePoints[i][0],
                y: polylinePoints[i][1]
            };
            C = {
                x: polylinePoints[0][0],
                y: polylinePoints[0][1]
            };
        } else {
            B = {
                x: polylinePoints[i][0],
                y: polylinePoints[i][1]
            };
            C = {
                x: polylinePoints[i + 1][0],
                y: polylinePoints[i + 1][1]
            };
        }
        //计算角度
        const angleA = Math.acos((Math.pow(getDistence(A, C), 2) + Math.pow(getDistence(A, B), 2) - Math.pow(getDistence(B, C), 2)) / (2  getDistence(A, C)  getDistence(A, B)))
        totalA += angleA
    }
    //判断角度之和
    return totalA === 2  Math.PI
}

const checkPointInPolyline = (point, polylinePoints) => {
    //射线法
  let leftSide = 0;
  const A = point;
  for (let i = 0; i < polylinePoints.length; i++) {
    let B, C;
    if (i === polylinePoints.length - 1) {
      B = {
        x: polylinePoints[i][0],
        y: polylinePoints[i][1]
      };
      C = {
        x: polylinePoints[0][0],
        y: polylinePoints[0][1]
      };
    } else {
      B = {
        x: polylinePoints[i][0],
        y: polylinePoints[i][1]
      };
      C = {
        x: polylinePoints[i + 1][0],
        y: polylinePoints[i + 1][1]
      };
    }
    //判断左侧相交
    let sortByY = [B.y, C.y].sort((a,b) => a-b)
    if (sortByY[0] < A.y && sortByY[1] > A.y){
      if(B.x<A.x || C.x < A.x){
        leftSide++
      }
    }
  }
  return leftSide % 2 === 1
}