站長資訊網(wǎng)數(shù)據(jù)庫是屬于服務(wù)器的，這是天經(jīng)地義的事，但是有時(shí)候數(shù)據(jù)也許并非需要存儲(chǔ)在服務(wù)器，但是這些數(shù)據(jù)也是一條一條的記錄，怎么辦？今天來帶領(lǐng)你領(lǐng)略一下H5的一個(gè)新特性–indexedDB的風(fēng)騷。你會(huì)情不自禁的發(fā)出感嘆–不可思議！
一、鏈接數(shù)據(jù)庫
indexedDB沒有創(chuàng)建數(shù)據(jù)庫的概念，你可以直接鏈接數(shù)據(jù)庫，如果你鏈接的數(shù)據(jù)庫并不存在，那么會(huì)自動(dòng)的創(chuàng)建一個(gè)數(shù)據(jù)庫?？聪旅娴倪@個(gè)例子。
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Document</title></head><body><button type="" id='conbtn'>鏈接數(shù)據(jù)庫</button><script>// In the following line, you should include the prefixes of implementations you want to test. window.indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB; // DON'T use "var indexedDB = ..." if you're not in a function. // Moreover, you may need references to some window.IDB* objects: window.IDBTransaction = window.IDBTransaction || window.webkitIDBTransaction || window.msIDBTransaction; window.IDBKeyRange = window.IDBKeyRange || window.webkitIDBKeyRange || window.msIDBKeyRange // (Mozilla has never prefixed these objects, so we don't need window.mozIDB*) function connectDB(name,version,success,error){ let dbConnect = indexedDB.open(name,version); dbConnect.onsuccess = function(e){ console.log('數(shù)據(jù)庫鏈接成功！'); success(e.target.result); } dbConnect.onerror = function(e){ console.log('數(shù)據(jù)庫鏈接失?。?#39;); error(e); } dbConnect.onupgradeneeded = function(e){ success(e.target.result); let oldVersion = e.oldVersion; let newVersion = e.newVersion; console.log('數(shù)據(jù)庫更新成功，舊的版本號為：'+oldVersion+",新的版本號為："+newVersion); } } window.onload=function(){ let btn = document.getElementById('conbtn'); btn.onclick = function(){ connectDB('haha',1,function(){ console.log('鏈接成功，或者更新成功回調(diào)函數(shù)'); },function(){ console.log('鏈接失敗回調(diào)函數(shù)！') }); } }</script></body></html>
我點(diǎn)了兩次鏈接數(shù)據(jù)庫，結(jié)果是這樣的。
在Application的indexedDB中我們發(fā)現(xiàn)多了一個(gè)東西。
可以看到haha數(shù)據(jù)庫已經(jīng)成功建立了。
indexedDB的open方法用來鏈接或者更新數(shù)據(jù)庫，第一次創(chuàng)建也認(rèn)為是一次更新。第一個(gè)參數(shù)是數(shù)據(jù)庫的名字，第二個(gè)參數(shù)為版本號。第一次創(chuàng)建或者版本號發(fā)生改變時(shí)出發(fā)更新事件upgradeneeded，鏈接成功后出發(fā)success事件，鏈接出錯(cuò)時(shí)觸發(fā)error事件。
二、建表和索引
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Document</title></head><body><button type="" id='conbtn'>鏈接數(shù)據(jù)庫</button><script>// In the following line, you should include the prefixes of implementations you want to test. window.indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB; // DON'T use "var indexedDB = ..." if you're not in a function. // Moreover, you may need references to some window.IDB* objects: window.IDBTransaction = window.IDBTransaction || window.webkitIDBTransaction || window.msIDBTransaction; window.IDBKeyRange = window.IDBKeyRange || window.webkitIDBKeyRange || window.msIDBKeyRange // (Mozilla has never prefixed these objects, so we don't need window.mozIDB*) function connectDB(name,version,success,update,error){ let dbConnect = indexedDB.open(name,version); dbConnect.onsuccess = function(e){ console.log('數(shù)據(jù)庫鏈接成功！'); success(e.target.result); } dbConnect.onerror = function(e){ console.log('數(shù)據(jù)庫鏈接失??！'); error(e); } dbConnect.onupgradeneeded = function(e){ update(e.target.result); let oldVersion = e.oldVersion; let newVersion = e.newVersion; console.log('數(shù)據(jù)庫更新成功，舊的版本號為：'+oldVersion+",新的版本號為："+newVersion); } } function createTable(idb,storeName,key,idxs){if(!idb){ console.log(idb);return ; }if(!key || !idxs){ console.log('參數(shù)錯(cuò)誤');return ; }if(!storeName){ console.log('storeName必須');return ; }try{var store = idb.createObjectStore(storeName,key); console.log('數(shù)據(jù)庫存儲(chǔ)對象(table)創(chuàng)建成功');for(var i = 0;i<idxs.length;i++){var idx = idxs[i]; store.createIndex(idx.indexName,idx.keyPath,idx.optionalParameters); console.log('索引'+idx.indexName+'創(chuàng)建成功'); } }catch(e){ console.log('建表出現(xiàn)錯(cuò)誤'); console.log(JSON.stringify(e)) } } window.onload=function(){ let btn = document.getElementById('conbtn'); btn.onclick = function(){ connectDB('haha',1, function(idb){ console.log('鏈接成功，或者更新成功回調(diào)函數(shù)'); },function(idb){ createTable(idb,'test',{keyPath:'id',autoIncrement:true},[ { indexName:'testIndex', keyPath:'name', optionalParameters:{ unique:true, multiEntry:false }}]); },function(){ console.log('鏈接失敗回調(diào)函數(shù)！') }); } }</script></body></html>
我點(diǎn)了一下按鈕結(jié)果時(shí)這樣的。
這里用到的兩個(gè)核心方法時(shí)createObjectStore，和createIndex,這兩個(gè)方法必須在數(shù)據(jù)庫發(fā)生更新的事件中執(zhí)行。
createObjectStore方法可以理解成是創(chuàng)建表，接受第一個(gè)參數(shù)為一個(gè)字符串，表示表名，第二個(gè)參數(shù)是一個(gè)對象，指定主鍵相關(guān)的東西，{keyPath:'主鍵是哪個(gè)字段',autoIncrement:是否自增}。
createIndex方法是創(chuàng)建索引的，接受三個(gè)參數(shù)，第一個(gè)是一個(gè)字符串，表示索引的名字，第二個(gè)參數(shù)表示字段名（誰的索引），第三個(gè)參數(shù)是個(gè)對象，具體自己查去。索引的作用是在查詢操作時(shí)可以用到，不詳講，自行g(shù)oogle吧。
三、添加數(shù)據(jù)
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Document</title></head><body><button type="" id='conbtn'>鏈接數(shù)據(jù)庫</button><button type="" id='add'>添加數(shù)據(jù)</button><script>// In the following line, you should include the prefixes of implementations you want to test. window.indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB; // DON'T use "var indexedDB = ..." if you're not in a function. // Moreover, you may need references to some window.IDB* objects: window.IDBTransaction = window.IDBTransaction || window.webkitIDBTransaction || window.msIDBTransaction; window.IDBKeyRange = window.IDBKeyRange || window.webkitIDBKeyRange || window.msIDBKeyRange // (Mozilla has never prefixed these objects, so we don't need window.mozIDB*) function connectDB(name,version,success,update,error){ let dbConnect = indexedDB.open(name,version); dbConnect.onsuccess = function(e){ console.log('數(shù)據(jù)庫鏈接成功！'); success(e.target.result); } dbConnect.onerror = function(e){ console.log('數(shù)據(jù)庫鏈接失?。?#39;); error(e); } dbConnect.onupgradeneeded = function(e){ update(e.target.result); let oldVersion = e.oldVersion; let newVersion = e.newVersion; console.log('數(shù)據(jù)庫更新成功，舊的版本號為：'+oldVersion+",新的版本號為："+newVersion); } } function createTable(idb,storeName,key,idxs){if(!idb){ console.log(idb);return ; }if(!key || !idxs){ console.log('參數(shù)錯(cuò)誤');return ; }if(!storeName){ console.log('storeName必須');return ; }try{var store = idb.createObjectStore(storeName,key); console.log('數(shù)據(jù)庫存儲(chǔ)對象(table)創(chuàng)建成功');for(var i = 0;i<idxs.length;i++){var idx = idxs[i]; store.createIndex(idx.indexName,idx.keyPath,idx.optionalParameters); console.log('索引'+idx.indexName+'創(chuàng)建成功'); } }catch(e){ console.log('建表出現(xiàn)錯(cuò)誤'); console.log(JSON.stringify(e)) } }function add(storeName,values){ connectDB('haha',1,function(idb){var ts = idb.transaction(storeName,"readwrite");var store = ts.objectStore(storeName); for(var i = 0;i<values.length;i++){ (function(i){var value = values[i];var req = store.put(value); req.onsuccess = function(){ console.log("添加第"+i+"個(gè)數(shù)據(jù)成功"); } req.onerror = function(e){ console.log("添加第"+i+"個(gè)數(shù)據(jù)失敗"); console.log(JSON.stringify(e)); } })(i) } ts.oncomplete = function(){ console.log('添加數(shù)據(jù)事務(wù)結(jié)束！'); } },function(){},function(){}); } window.onload=function(){ let btn = document.getElementById('conbtn'); btn.onclick = function(){ connectDB('haha',1, function(idb){ console.log('鏈接成功，或者更新成功回調(diào)函數(shù)'); },function(idb){ createTable(idb,'test',{keyPath:'id',autoIncrement:true},[ { indexName:'testIndex', keyPath:'name', optionalParameters:{ unique:true, multiEntry:false }}]); },function(){ console.log('鏈接失敗回調(diào)函數(shù)！') }); } let add1 = document.getElementById('add'); add1.onclick = function(){ add('test',[{name:"fjidfji",a:'uuuu'}]) } }</script></body></html>
比較神奇的是你在建表的時(shí)候不需要指定你的字段，再添加數(shù)據(jù)時(shí)可以隨便加。添加數(shù)據(jù)用到的是表對象的put方法，之前需要一個(gè)事務(wù)，從事務(wù)調(diào)個(gè)方法拿到存儲(chǔ)對象（可以理解為表），具體看看例子就明白了。
四、查詢數(shù)據(jù)
Document鏈接數(shù)據(jù)庫添加數(shù)據(jù)查詢
查詢操作主要用到了游標(biāo)，這個(gè)說起來還比較多，沒時(shí)間說了，自行g(shù)oogle。還有很多的操作這里不講了。給一個(gè)我封裝的不是很好的簡易庫，僅供參考。
一個(gè)簡易庫。
(function(window){'use strict'; window.dbUtil={ indexedDB :(window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB), IDBTransaction :(window.IDBTransaction || window.webkitIDBTransaction || window.msIDBTransaction), IDBKeyRange :(window.IDBKeyRange || window.webkitIDBKeyRange || window.msIDBKeyRange), IDBCursor : (window.IDBCursor || window.webkitIDBCursor || window.msIDBCursor), idb:null, dbName:"", dbVersion:"",/** * 初始化數(shù)據(jù)庫，創(chuàng)建表和建立鏈接 * @param {[type]} dbName [description] * @param {[type]} dbVersion [description] * @param {[type]} storeObjs [description] * @return {[type]} [description] */initDB:function (dbName,dbVersion,storeObjs){this.dbName = dbName;this.dbVersion = dbVersion;var dbConnect = this.indexedDB.open(this.dbName,this.dbVersion);var self = this; dbConnect.onsuccess = function(e){ self.idb = e.target.result; self.log('數(shù)據(jù)庫鏈接成功！'); } dbConnect.onerror = function(e){ console.log(e) self.log('數(shù)據(jù)庫鏈接失敗!'); } dbConnect.onupgradeneeded = function(e){ self.idb = e.target.result;var ts = e.target.transaction;var oldVersion = e.oldVersion;var newVersion = e.newVersion; self.log('數(shù)據(jù)庫更新成功，舊的版本號為：'+oldVersion+",新的版本號為："+newVersion);if(storeObjs){for(var k = 0,len=storeObjs.length;k<len;k++){var storeObj = storeObjs[k];var storeName = storeObj.storeName;var key = storeObj.key;var idxs = storeObj.idxs; self.createTable(storeName,key,idxs) } } } },/** * 創(chuàng)建數(shù)據(jù)庫存儲(chǔ)對象（表） * @param {[type]} key [description] * @param {[type]} [description] * @return {[type]} [description] */createTable:function(storeName,key,idxs){var self = this;var idb = self.idb;if(!idb){ self.log('數(shù)據(jù)庫沒有鏈接');return ; }if(!key || !idxs){ self.log('參數(shù)錯(cuò)誤');return ; }if(!storeName){ self.log('storeName必須');return ; }try{var store = idb.createObjectStore(storeName,key); self.log('數(shù)據(jù)庫存儲(chǔ)對象(table)創(chuàng)建成功');for(var i = 0;i<idxs.length;i++){var idx = idxs[i]; store.createIndex(idx.indexName,idx.keyPath,idx.optionalParameters); self.log('索引'+idx.indexName+'創(chuàng)建成功'); } }catch(e){ self.log('建表出現(xiàn)錯(cuò)誤'); console.log(JSON.stringify(e)) } },/** * [add description] * @param {[type]} storeName [description] * @param {[type]} values [description] */add:function(storeName,values){var dbConnect = this.indexedDB.open(this.dbName,this.dbVersion);var self = this; dbConnect.onsuccess = function(e){var idb = e.target.result;var ts = idb.transaction(storeName,"readwrite");var store = ts.objectStore(storeName);for(var i = 0;i<values.length;i++){ (function(i){var value = values[i];var req = store.put(value); req.onsuccess = function(){ self.log("添加第"+i+"個(gè)數(shù)據(jù)成功"); } req.onerror = function(e){ self.log("添加第"+i+"個(gè)數(shù)據(jù)失敗"); self.log(JSON.stringify(e)); } })(i) } ts.oncomplete = function(){ self.log('添加數(shù)據(jù)事務(wù)結(jié)束！'); } } },/** * [select description] * @param {[type]} storeName [description] * @param {[type]} count [description] * @param {Function} callback [description] * @param {[type]} indexName [description] * @return {[type]} [description] */select:function(storeName,count,callback,indexName){var dbConnect = this.indexedDB.open(this.dbName,this.dbVersion);var self = this;var total = 0;var data = []; dbConnect.onsuccess = function(e){ self.log("數(shù)據(jù)庫鏈接成功！");var idb = e.target.result;var ts = idb.transaction(storeName,"readonly");var store = ts.objectStore(storeName);var req = store.count();var req2 = null; req.onsuccess = function(){ total = this.result;var realCount = (count<=total)?count:total;if(typeof indexName == 'undefined'){var range = IDBKeyRange.bound(0,"9999999999999999999999"); req2 = store.openCursor(range,'prev');var cc = 0; req2.onsuccess = function(){var cursor = this.result;if(total == 0){ callback([]);return; }if(cursor){ cc++; data.push(cursor.value);if(cc==realCount){ callback(data);return; } cursor.continue(); } } req2.onerror = function(){ self.log("檢索出錯(cuò)") } }else{//待寫 } } } },/** * [delete description] * @param {[type]} storeName [description] * @param {[type]} key [description] * @return {[type]} [description] */delete:function(storeName,key,callback){var dbConnect = this.indexedDB.open(this.dbName,this.dbVersion); let self = this; dbConnect.onsuccess = function(e){var idb = e.target.result;var ts = idb.transaction(storeName,'readwrite');var store = ts.objectStore(storeName); store.delete(key); self.log('刪除成功！');if(callback){ callback(); } } },/** * [funciton description] * @param {[type]} storeName [description] * @param {[type]} key [description] * @param {[type]} existCall [description] * @param {[type]} notExistCall [description] * @return {[type]} [description] */isExist:function(storeName,key,existCall,notExistCall){var dbConnect = this.indexedDB.open(this.dbName,this.dbVersion); dbConnect.onsuccess = function(e){var idb = e.target.result;var ts = idb.transaction(storeName,'readonly');var store = ts.objectStore(storeName);var req = store.get(key); req.onsuccess = function(){if(this.result == undefined){ notExistCall(); }else{ existCall(this.result); } } req.onerror = function(){ notExistCall(); } } },/** * clear * @param {[type]} storeName [description] * @return {[type]} [description] */clear:function clearObjectStore(storeName){var dbConnect = this.indexedDB.open(this.dbName,this.dbVersion); dbConnect.onsuccess = function(e){var idb = e.target.result;var ts = idb.transaction(storeName,'readwrite');var store = ts.objectStore(storeName); store.clear(); } },/** * 刪除數(shù)據(jù)庫 * @param {[type]} dbName [description] * @return {[type]} [description] */dropDatabase:function(dbName){this.indexedDB.deleteDatabase(dbName);this.log('成功刪除數(shù)據(jù)庫:'+dbName); },/** * [log description] * @param {[type]} msg [description] * @return {[type]} [description] */log:function(msg){ console.log((new Date()).toTimeString()+":"+msg) } } })(window);
五、使用indexedDB的優(yōu)缺點(diǎn)
1、優(yōu)點(diǎn)：可以將一些數(shù)據(jù)放到瀏覽器端，不用和服務(wù)器交互就可以實(shí)現(xiàn)一些功能，減輕服務(wù)器負(fù)擔(dān)，加快響應(yīng)速度。
2、缺點(diǎn)：
(1)不可靠：用戶可能刪處indexedDB，而且更換瀏覽器或者設(shè)備后這些數(shù)據(jù)就沒了。
2）不便于數(shù)據(jù)采集：有很多時(shí)候?qū)?shù)據(jù)存到服務(wù)器是為了獲得一些數(shù)據(jù)，如果放到瀏覽器端，這些數(shù)據(jù)比較難獲取。
（3）無法共享：不同用戶沒辦法共享數(shù)據(jù)，甚至?xí)r一個(gè)設(shè)備的不同瀏覽器也沒法共享。
所以，是否適用indexedDB要進(jìn)行一下利弊權(quán)衡，不是有了indexedDB就啥也不管，一骨腦將數(shù)據(jù)放進(jìn)去。
最近兩個(gè)課程設(shè)計(jì)，還有面試， 文章寫的比較匆忙，如有問題請各位園友批評指正。最近找實(shí)習(xí)，各位園友要是我寫的東西還可以而且公司招聘實(shí)習(xí)生的話可以給大熊一個(gè)機(jī)會(huì)，謝謝！
