How to determine whether a shape is convex in js (code)

The content of this article is about how js determines whether a shape is convex (code). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

 //--------------判断是否是凸多边形函数-------------------------
  // p：顶点数组(数组对象) n：顶点个数；1：凸集；-1：凹集；0：曲线不符合要求无法计算
  function convex(p,n) {
      var j,k,z;      
      var flag = 0;      
      if (n<3){       
       // console.log("不符合要求")
        return 0;
      }      
      for (var i=0;i<n;i++) {
          j = (i + 1) % n;
          k = (i + 2) % n;
          z = (p[j].x - p[i].x) * (p[k].y - p[j].y);
          z -= (p[j].y - p[i].y) * (p[k].x - p[j].x);          
          if (z < 0){
            flag |= 1;
          } else if (z > 0){
            flag |=  2;
          }          
          if (flag == 3){            
          // console.log("凹多边形，不符合要求")
            return -1; //CONCAVE
          }
      }      
      if (flag != 0){          
      // console.log("凸多边形")
          return 1; //CONVEX
      } else{          return 0;
      }
  }

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