JavaScript实现的Map

/*
=====================================================================
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disclaimer.
 
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THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
@author Daniel Kwiecinski <daniel.kwiecinski@lambder.com>
@copyright 2009 Daniel Kwiecinski.
@end
=====================================================================
*/
var HashMap = function() {
  this.initialize();
}
 
HashMap.prototype = {
  hashkey_prefix: "<#HashMapHashkeyPerfix>",
  hashcode_field: "<#HashMapHashcodeField>",
  hashmap_instance_id: 0,
 
  initialize: function() {
    this.backing_hash = {};
    this.code = 0;
    this.hashmap_instance_id += 1;
    this.instance_id = this.hashmap_instance_id;
  },
 
  hashcodeField: function() {
    return this.hashcode_field + this.instance_id;
  },
  /*
maps value to key returning previous assocciation
*/
  put: function(key, value) {
    var prev;
    if (key && value) {
      var hashCode;
      if (typeof(key) === "number" || typeof(key) === "string") {
        hashCode = key;
      } else {	   
        hashCode = key[this.hashcodeField()];
      }
      if (hashCode) {
        prev = this.backing_hash[hashCode];
      } else {
        this.code += 1;
        hashCode = this.hashkey_prefix + this.code;
        key[this.hashcodeField()] = hashCode;
      }
      this.backing_hash[hashCode] = [key, value];
    }
    return prev === undefined ? undefined : prev[1];
  },
  /*
returns value associated with given key
*/
  get: function(key) {
    var value;
    if (key) {
      var hashCode;
      if (typeof(key) === "number" || typeof(key) === "string") {
        hashCode = key;
      } else {
        hashCode = key[this.hashcodeField()];
      }
      if (hashCode) {
        value = this.backing_hash[hashCode];
      }
    }
    return value === undefined ? undefined : value[1];
  },
  /*
deletes association by given key.
Returns true if the assocciation existed, false otherwise
*/
  del: function(key) {
    var success = false;
    if (key) {
      var hashCode;
      if (typeof(key) === "number" || typeof(key) === "string") {
        hashCode = key;
      } else {
        hashCode = key[this.hashcodeField()];
      }
      if (hashCode) {
        var prev = this.backing_hash[hashCode];
        this.backing_hash[hashCode] = undefined;
        if (prev !== undefined){
          key[this.hashcodeField()] = undefined; //let's clean the key object
          success = true;
        }
      }
    }
    return success;
  },
  /*
iterate over key-value pairs passing them to provided callback
the iteration process is interrupted when the callback returns false.
the execution context of the callback is the value of the key-value pair
@ returns the HashMap (so we can chain) (
*/
  each: function(callback, args) {
    var key;
    for (key in this.backing_hash){
      if (callback.call(this.backing_hash[key][1], this.backing_hash[key][0], this.backing_hash[key][1]) === false)
        break;
    }
    return this;
  },
  toString: function() {
    return "HashMapJS"
  }
 
}