javascript 判断点在面内，点在圆内

傷城~ 2022-01-30 05:55 297阅读 0赞

点在多边形内常用的算法就是使用射线法，作为笔记直接上代码：

/** 
         *  判断一个点是否在多边形内部 
         *  @param points 多边形坐标集合 
         *  @param testPoint 测试点坐标 
         *  返回true为真，false为假 
         *  */  
    	    function insidePolygon(points, testPoint){  
    	        var x = testPoint[0], y = testPoint[1];  
    	        var inside = false;  
    	        for (var i = 0, j = points.length - 1; i < points.length; j = i++) {  
    	            var xi = points[i][0], yi = points[i][1];  
    	            var xj = points[j][0], yj = points[j][1];  
    	  
    	            var intersect = ((yi > y) != (yj > y))  
    	                    && (x < (xj - xi) * (y - yi) / (yj - yi) + xi);  
    	            if (intersect) inside = !inside;  
    	        }  
    	        return inside;  
    	    }

点在圆内：

/** 
         *  判断一个点是否在圆的内部 
         *  @param point  测试点坐标 
         *  @param circle 圆心坐标 
         *  @param r 圆半径 
         *  返回true为真，false为假 
         *  */  
        function pointInsideCircle(point, circle, r) {  
            if (r===0) return false  
            var dx = circle[0] - point[0]  
            var dy = circle[1] - point[1]  
            return dx * dx + dy * dy <= r * r  
        }
    
    
    //或：
    	document.onclick = function(e) { 
    	 var r = 50; 		//半径
    	 var x1 = 100;
    	 var y1 = 100;
    	 var x2= e.clientX;
    	 var y2= e.clientY; 
    	 var distance = Math.abs(Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2))); 
    	 if (distance <= 50)
    	 alert("Yes!"); 
    }