本文實例講述了JavaScript使用享元模式實現(xiàn)文件上傳優(yōu)化操作。分享給大家供大家參考，具體如下：

一、享元模式是一種用于性能優(yōu)化的模式，主要優(yōu)化方式為，若系統(tǒng)中因為創(chuàng)建了大量類似的對象而導(dǎo)致內(nèi)存占用過高，則可以考慮使用享元模式實現(xiàn)。

二、實例說明：

如果在瀏覽器中上傳文件，若使用常規(guī)寫法， 每上傳一個文件，就會創(chuàng)建一個實例對象；如果上傳2000個文件，那就有2000個對象，瀏覽器很可能出現(xiàn)假死狀態(tài)。這種情況下，我們考慮適應(yīng)享元模式。

三、實例：

var Upload = function( uploadType ){  this.uploadType = uploadType;};Upload.prototype.delFile = function( id ){  uploadManager.setExternalState( id, this );  if( this.fileSize < 300 ){   return this.dom.parentNode.removeChild( this.dom );  }  if( window.confirm('確定要刪除該文件嗎？' + this.fileName )){     return this.dom.parentNode.removeChild( this.dom);  }};var UploadFactory = (function(){  var createdFlyWeightObjs = {};  return {    create: function( uploadType ){      if(createFlyWeightObjs[uploadType]){        return createdFlyWeightObjs[uploadType];      }      return createdFlyWeightObjs[uploadType] = new Upload(uploadType);    }  }})();var uploadManager = (function(){  var uploadDatabase = {};  return{    add: function(id, uploadType, fileName, fileSize){      var flyWeightObj = UploadFactory.create( uploadType );      var dom = document.createElement( 'div' );      dom.innerHTML = '<span>文件名稱：'+fileName+'，文件大小：' +fileSize + '</span>' + '<button class="delFile">刪除</button>';      dom.querySelector( ".delFile" ).onclick = function(){       flyWeightObj.delFile( id );       document.body.appendChild( dom );       uploadDatabase[ id ] = {         fileName: fileName,         fileSize: fileSize,         dom: dom       };       return flyWeightObj;     },     setExternalState: functon( id, flyWeightObj ){        var uploadData = uploadDatabase[ id ];        for( var i in uploadData){           flyWeightObj[ i ] = uploadData[ i ];        }     }  }})();

然后需要寫一個觸發(fā)上傳動作的startUpload函數(shù)：

var id = o;window.startUpload = function( uploadType, files ){  for( var i=0,file; file = fules[ i ++ ];){     var uploadObj = uploadManger.add( ++id, uploadType, file.fileName, file.fileSize );  }};

最后調(diào)用，如下：

startUpload( 'plugin', [  {    fileName: '1.txt',    fileSize: 1000   },   {     fileName: '2.html',     fileSize: 1000   },   {     fileName: '3.txt',     fileSize: 5000   }]);startUpload( 'flash', [  {    fileName: '4.txt',    fileSize: 1000   },   {     fileName: '5.html',     fileSize: 1000   },   {     fileName: '6.txt',     fileSize: 5000   }]);

四、解釋：