js map

var map = {}; // Map map = new HashMap();

map[key] = value; // map.put(key, value);

var value = map[key]; // Object value = map.get(key);

var has = key in map; // boolean has =map.containsKey(key);

delete map[key]; // map.remove(key);

// 遍历  

for(key in map){  

    alert(key + map[key]); 

}  

//长度判断

var length   = Object.keys(map).length ;

来自： http://blog.sina.com.cn/s/blog_6b8660320101iun9.html
            http://stackoverflow.com/questions/5223/length-of-javascript-object-ie-associative-array