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HTML5 網(wǎng)頁存儲 Web Storage
一、認(rèn)識Web Storage
Web Storage是一種將少量數(shù)據(jù)存儲在客戶端(client)磁盤的技術(shù)。只要支持WebStorage API規(guī)格的瀏覽器,網(wǎng)頁設(shè)計者都可以使用JavaScript來操作它,我們先了解一下Web Storage。
Web Storage的容量由客戶端瀏覽器決定,通常1MB~5MB。
Web Storage純粹運(yùn)行客戶端,不會每次網(wǎng)頁請求連帶發(fā)送給服務(wù)端。
Web Storage以一組key-value對應(yīng)保存數(shù)據(jù)。
Web Storage提供兩種方式將數(shù)據(jù)保存在客戶端:一種是localStorage,一種是sessionStorage,兩者的差異在于申明周期和有效范圍。
Web Storage類型 | 生命周期 | 有效范圍 |
localStorage | 執(zhí)行刪除命令時才會消失 | 同一網(wǎng)站的網(wǎng)頁可以跨窗口和分頁 |
sessionStorage | 瀏覽器窗口或分頁(tab)關(guān)閉就會消失 | 僅對當(dāng)前瀏覽器窗口或分頁有效 |
檢測瀏覽器是否支持Web Storage,語法如下:
if(typeof(Storage)=="undefined"){ <span style="white-space:pre"> </span>alert("您的瀏覽器不支持Web Storage"); } else{ <span style="white-space:pre"> </span>//localStorage和sessionStorage程序代碼 }
注意:IE和Firefox測試時需要把文件上傳到服務(wù)器或者localhost才能運(yùn)行。建議測試時使用Google Chrome瀏覽器。
二、具體學(xué)習(xí)
1、訪問localStorage
相同網(wǎng)站是指:協(xié)議、主機(jī)(domain與ip)、傳輸端口(port)都必須相同。
WebStorage只允許存儲字符串?dāng)?shù)據(jù),有以下3種訪問localStorage的方法,前面的window可以不寫
Storage對象的setItem和getItem方法(key:"userdata",value:"Hello World")
存儲:window.localStorage.setItem(key,value);
讀取:var v = window.localStorage.getItem(key);
數(shù)組索引
存儲:window.localStorage[key] =value;
讀?。簐ar v = window.localStorage[key];
屬性
存儲:window.localStorage.key =value;
讀取:var v = window.localStorage.key;
<span style="font-size:14px;"><!DOCTYPE html> <html> <head> <title>網(wǎng)頁存儲localStorage</title> <script type="text/javascript"> function onLoad(){ if(typeof(Storage)=="undefined"){ alert("Sorry!你的瀏覽器不支持Web Storage"); } else{ btn_save.addEventListener("click",saveToLocalStorage); btn_load.addEventListener("click",loadFromLocalStorage); } } function saveToLocalStorage(){ <strong>localStorage.username = inputname.value;</strong> } function loadFromLocalStorage(){ <strong>show_LocalStorage.innerHTML = localStorage.username+"你好,歡迎來到我的網(wǎng)站!";</strong> } </script> </head> <body onload="onLoad()"> 請輸入你的姓名:<input type="text" id="inputname" value="" /><br/> <p id="show_LocalStorage"></p><br /> <button id="btn_save">存儲到localStorage</button> <button id="btn_load">從localStorage讀取數(shù)據(jù)</button> </body> </html></span><span style="font-size: 18px;"> </span>
二、刪除localStorage
要想刪除某一條localStorage數(shù)據(jù),可以調(diào)用removeItem方法或者delete屬性進(jìn)行刪除。
window.localStorage.removeItem("userdata");
delete window.localStorage.userdata;
delete.window.localStorage["userdata"];
要想刪除全部的localStorage數(shù)據(jù),可以使用clear()方法。
localStorage.clear();
<!DOCTYPE html> <html> <head> <title>網(wǎng)頁存儲localStorage</title> <script type="text/javascript"> function onLoad(){ if(typeof(Storage)=="undefined"){ alert("Sorry!你的瀏覽器不支持Web Storage"); } else{ btn_save.addEventListener("click",saveToLocalStorage); btn_load.addEventListener("click",loadFromLocalStorage); btn_clear.addEventListener("click",clearLocalStorage); } } function saveToLocalStorage(){ localStorage.username = inputname.value; } function loadFromLocalStorage(){ show_LocalStorage.innerHTML = localStorage.username+"你好,歡迎來到我的網(wǎng)站!"; } function clearLocalStorage(){ <strong>localStorage.clear();</strong> show_LocalStorage.innerHTML = localStorage.username; } </script> </head> <body onload="onLoad()"> 請輸入你的姓名:<input type="text" id="inputname" value="" /><br/> <p id="show_LocalStorage"></p><br /> <button id="btn_save">存儲到localStorage</button> <button id="btn_load">從localStorage讀取數(shù)據(jù)</button> <button id="btn_clear">清除localStorage數(shù)據(jù)</button> </body> </html>
三、訪問sessionStorage
存儲
window.sessionStorage.setItem(key,value);
window.sessionStorage [key] = [value];
window.sessionStorage.key= value;
讀取
var v = window.sessionStorage.getItem(key);
var v = window.sessionStorage [key];
var v = window.sessionStorage.key;
清除
window.sessionStorage.removeItem(key);
delete window.sessionStorage.key;
delete window.sessionStorage [key];
//全部清除
sessionStorage.clear();
<span style="font-size:14px;"><!DOCTYPE html> <html> <head> <title>網(wǎng)頁存儲sessionStorage</title> <script type="text/javascript"> function onLoad(){ inputSpan.style.display = 'none'; if(typeof(Storage)=="undefined"){ alert("Sorry!你的瀏覽器不支持Web Storage"); } else{ /*判斷姓名是否已經(jīng)存入localStorage,已存入時才執(zhí)行{ }內(nèi)的命令*/ if(localStorage.username){ /*數(shù)據(jù)不存在時返回undefined*/ if(!localStorage.counter){ localStorage.counter = 1; /*初始值設(shè)為1*/ } else{ localStorage.counter++; /*遞增*/ } btn_login.style.display = 'none'; /*隱藏“登錄”按鈕*/ show_LocalStorage.innerHTML = localStorage.username+"你好,這是你第"+localStorage.counter+"次來到網(wǎng)站"; } btn_login.addEventListener("click",login); btn_send.addEventListener("click",sendok); btn_logout.addEventListener("click",clearLocalStorage); } } function sendok(){ localStorage.username = inputname.value; location.reload(); /*重載網(wǎng)頁*/ } function login(){ inputSpan.style.display = ''; } function clearLocalStorage(){ localStorage.clear(); /*情況localStorage*/ show_LocalStorage.innerHTML = "已成功注銷!"; btn_login.style.display = ''; /*顯示“登錄”按鈕*/ inputSpan.style.display = ''; /*顯示姓名輸入框和“提交”按鈕*/ } </script> </head> <body onload="onLoad()"> <button id="btn_login">登錄</button> <button id="btn_logout">注銷</button><br /> <span id="inputSpan">請輸入你的姓名:<input type="text" id="inputname" value="" /><button id="btn_send">提交</button></span><br /> <p id="show_LocalStorage"></p><br /> </body> </html></span><span style="font-weight: bold; font-size: 24px;"> </span>
注:JavaScript里的運(yùn)算符“+”不僅可以數(shù)字相加還可以字符串相加。例如"123"+456="123456"
上例中l(wèi)ocalStorage.counter++;如果改成localStorage.counter = localStorage.counter +1;就會出現(xiàn)”11111......“
JavaScript將字符串轉(zhuǎn)換成為數(shù)字可以用Number()方法,localStorage.counter =Number(localStorage.counter )+1;
以上就是HTML5網(wǎng)頁存儲的相關(guān)知識的簡略介紹,當(dāng)然詳細(xì)使用上面的不同還得要大家自己使用過才領(lǐng)會。如果想了解更多,歡迎關(guān)注億速云行業(yè)資訊頻道哦!
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