  
            //不能构成三角形;
            if(side[0]+side[1]<=side[2] || side[0]+side[2]<=side[1] || side[1]+side[2]<=side[0]) return area; 
        
            //利用海伦公式。s=sqr(p*(p-a)(p-b)(p-c)); 
            const p = (side[0]+side[1]+side[2])/2; //半周长;
            area = Math.sqrt(p*(p-side[0])*(p-side[1])*(p-side[2])); 
            
            return area;
        }
    </script>
  </body>
</html>
