Google returned a good reference on the first search: http://diveintohtml5.org/storage.html
I wrote two sandbox programs with three buttons to demonstrate how to save, fetch, and delete. The first program handles a single string.
String demo
<!DOCTYPE HTML>
<html>
<head>
<title>HTML5 Persistent String</title>
<script type="text/javascript" charset="utf-8">
//---------------------------------------
// Button handlers
//---------------------------------------
function setit() {
var stringValue = "Hello World!";
localStorage.setItem("string_key", stringValue);
document.getElementById("stringResponseText").innerHTML =
"Set string value: " + stringValue;
}
function nullit() {
localStorage.setItem("string_key", null);
document.getElementById("stringResponseText").innerHTML =
"Set string value to null.";
}
function getit() {
var stringValue = localStorage.getItem("string_key");
document.getElementById("stringResponseText").innerHTML =
"Got string value: " + stringValue;
}
</script>
</head>
<body bgcolor="lightgreen">
<h2>HTML5 Persistent String</h2>
<input type="button" value="set" onclick="setit()" />
<input type="button" value="get" onclick="getit()" />
<input type="button" value="null" onclick="nullit()" />
<p>
<p id="stringResponseText"> </p>
</body>
</html>
Object demo
The second program follows the same pattern, but with a user-defined javascript object. The secret here is to use JSON.stringify to convert your object into a 'flat' string for saving, and JSON.parse() to reconstitute the object after it is read.
<!DOCTYPE HTML>
<html>
<head>
<title>HTML5 Persistent Object</title>
<script type="text/javascript" charset="utf-8">
//---------------------------------------
// Object definition and accessor
//---------------------------------------
function myObject(var1, var2, var3) {
this.one = var1;
this.two = var2;
this.three = var3;
this.toString = toString;
}
function toString() {
return "one=" + this.one +
" two=" + this.two +
" three=" + this.three;
}
//---------------------------------------
// Button handlers.
//---------------------------------------
function setIt() {
var testObject = new myObject( "bird", "cat", "dog" );
localStorage.setItem("object_key", JSON.stringify(testObject));
document.getElementById("objectResponseText").innerHTML =
"Set object value: " + testObject.toString();
}
function nullIt() {
localStorage.setItem("object_key", null);
document.getElementById("objectResponseText").innerHTML =
"Set object value to null.";
}
function getIt() {
var stringifiedObject = localStorage.getItem("object_key");
var reconstitutedObject = JSON.parse(stringifiedObject);
if (reconstitutedObject) {
reconstitutedObject.toString = toString;
document.getElementById("objectResponseText").innerHTML =
"Got object value: " + reconstitutedObject.toString();
}
else {
document.getElementById("objectResponseText").innerHTML =
"Object value not found.";
}
}
</script>
</head>
<body bgcolor="lightblue">
<h1>HTML5 Persistent Object</h1>
<h3>Object</h3>
<input type="button" value="set" onclick="setIt()" />
<input type="button" value="get" onclick="getIt()" />
<input type="button" value="null" onclick="nullIt()" />
<p>
<p id="objectResponseText"> </p>
</body>
</html>
Testing
These sandbox programs can be browsed directly with a browser which supports HTML5, such as Chrome or Safari.
They can also be bundled into a PhoneGap app (via index.html), where they will work well installed on a mobile device.
Hope this is useful!
Thanks for simple and concise explanation!
ReplyDeleteSaved me an hour!
is it possible to save a JS-file into localStorage or filesystem and use it?
ReplyDelete