js-对象赋值小细节

			var a = {n:2};
			var b = {m:3};
			var obj = {};
			obj[a] = 4; 
			obj[b] = 5;
			//key 一定是字符串  
			//那么a.toString() =  '[object Object]' ,b同理
			//即obj['[object Object]'] 
			console.log(a.toString())//[object Object]
			console.log(b.toString())//[object Object]
			console.log(obj[a]) //5