javascript 实现java中的Map

2022-09-26 11:14:56

javascript实现java中的Map，代码是在国外的一个网站上看到的（http://*.com/questions/368280/javascript-hashmap-equivalent），自己稍作了修改，之前也看到过有人用2个数组实现了Map，但是我感觉效率比较低，现在这个我感觉效率还可以，自己做了下测试，代码如下：
Map.js

Java代码

function Map(linkItems) {
this.current = undefined;
this._size = 0;
if(linkItems === false){
this.disableLinking();
}
}
/**
* 获取当前map
* @return 当前对象
*/
Map.noop = function() {
return this;
};
/**
* 非法操作
* @return
*/
Map.illegal = function() {
throw new Error("非法操作，Map已经被禁用");
};
/**
*
* @param obj
* @param foreignKeys
* @return
*/
Map.from = function(obj, foreignKeys) {
var map = new Map;
for(var prop in obj) {
if(foreignKeys || obj.hasOwnProperty(prop)){
map.put(prop, obj[prop]);
}
}
return map;
};
/**
* 禁用map
* @return
*/
Map.prototype.disableLinking = function() {
this.link = Map.noop;
this.unlink = Map.noop;
this.disableLinking = Map.noop;
this.next = Map.illegal;
this.key = Map.illegal;
this.value = Map.illegal;
this.clear = Map.illegal;
return this;
};
/**
* 返回hash值例如：number 123
* @param value key/value
* @return
*/
Map.prototype.hash = function(value) {
return (typeof value) + ‘ ‘ + (value instanceof Object ? (value.__hash || (value.__hash = ++arguments.callee.current)) : value.toString());
};
/**
* 返回map的长度
* @return
*/
Map.prototype.size = function() {
return this._size;
};
Map.prototype.hash.current = 0;
/**
* 通过key获取value
* @param key
* @return
*/
Map.prototype.get = function(key) {
var item = this[this.hash(key)];
return item === undefined ? undefined : item.value;
};
/**
* 向map中添加数据
* @param key 键
* @param value 值
* @return
*/
Map.prototype.put = function(key, value) {
var hash = this.hash(key);
if(this[hash] === undefined) {
var item = { key : key, value : value };
this[hash] = item;
this.link(item);
++this._size;
}else{
this[hash].value = value;
}
return this;
};
/**
* 通过key删除数据
* @param key
* @return
*/
Map.prototype.remove = function(key) {
var hash = this.hash(key);
var item = this[hash];
if(item !== undefined) {
--this._size;
this.unlink(item);
delete this[hash];
}
return this;
};
/**
* 清除map
* @return
*/
Map.prototype.clear = function() {
while(this._size){
this.remove(this.key());
}
return this;
};
/**
* 处理队列
* @param item
* @return
*/
Map.prototype.link = function(item) {
if(this._size == 0) {
item.prev = item;
item.next = item;
this.current = item;
}else {
item.prev = this.current.prev;
item.prev.next = item;
item.next = this.current;
this.current.prev = item;
}
};
Map.prototype.unlink = function(item) {
if(this._size == 0){
this.current = undefined;
}else {
item.prev.next = item.next;
item.next.prev = item.prev;
if(item === this.current){
this.current = item.next;
}
}
};
/**
* 获取下一个
* @return
*/
Map.prototype.next = function() {
this.current = this.current.next;
return this;
};
/**
* 获取key
* @return
*/
Map.prototype.key = function() {
return this.current.key;
};
/**
* 获取value
* @return
*/
Map.prototype.value = function() {
return this.current.value;
};