//定義點的結構體
function point(){
 this.x=0;
 this.y=0;
}
 
//計算一個點是否在多邊形里,參數:點,多邊形數組 
function PointInPoly(pt, poly) { 
    for (var c = false, i = -1, l = poly.length, j = l - 1; ++i < l; j = i) 
        ((poly[i].y <= pt.y && pt.y < poly[j].y) || (poly[j].y <= pt.y && pt.y < poly[i].y)) 
        && (pt.x < (poly[j].x - poly[i].x) * (pt.y - poly[i].y) / (poly[j].y - poly[i].y) + poly[i].x) 
        && (c = !c); 
    return c; 
}
 
 
 
//調用
 
var pt=new point();
pt.x=34.32812720562833;
pt.y=108.93115997314453;
//這里的下x，y坐標是多邊形的順時針的拐角節點來排序的
var _poly=[{x:1.1,y:1.1},{x:3,y:1},{x:6,y:4},{x:2,y:10},{x:1.1,y:1.1}];
 
 
var xx=PointInPoly(pt,_poly);
alert(xx);

原文鏈接：https://blog.csdn.net/tapist_Fps/article/details/121918541