API-localstorage&&sessionstorage
1.存儲形式:key——value
Localstorage永不過期,除非手動刪除
Sessionstorage瀏覽器關閉即數據消失
存儲流量,官方給出的解釋爲每個域名有5M大小
2.瀏覽器支持情況:
Ie8+,firefox3.5+,safari4.0+,chrome10.0+,opera10.6+,ios3.2+,android2.1+
3.localstorageAPI:
Getitem:取記錄
Setitem:存記錄
Removeitem:刪除記錄
Key:拿某個key值對應的數據
Clear:全部刪掉
4.Localstorage可以儲存的東西:
數組,json數據,圖片,腳本,樣式文件
5.使用方法:
Localstorage.setItem(“key1”,“value1”);
Var key2=Localstorage.key(“key2”);
6.存儲圖片:
Var url=”ncjdk.jpg”
Function set(key){
Var img=document.createElement(“img”);
img.addeventListener(“load”,function(){
//創建畫布
Var imgCanvas=document.createElement(“canvas”),
imgContext=imgcanvas.getcontext(“2d”);
//確保畫布的寬高和圖片一樣
imgCanvas.width=this.width;
imgCanvas.height=this.height;
//渲染圖片到畫布上
imgContext.drawImage(this,0,0,this.width,this.height);
//用urldata的形式取出
Var imgAsDataURL=imgCanvas.toDataURL(“image/png”);
//保存到本地存儲
Try{
localstorage.setItem(“key”,”imgAsDataURL”);
}catch(e){
Console.log(“storage failed”+e);
}
},false);
Img.src=src;
//從本地緩存獲取圖片並且渲染
Function get(key){
Var srcsStr=localstorage.getItem(key);
Var imgObj=document.createElement(“img”);
imgObj.src=srcStr;
document.body.appendChild(“imgObj”);
}