HTML5 client data storageWeb Storage—localStorage and sessionStorage

HTML5 provides a new method of storing data on the client side Web Storage
Similar to Cookie in HTML4
But it is much more powerful

Cookie

Let’s briefly review the cookies used before

Cookies store data on the user’s device. The amount of data stored is small, only 4KB
Yes Detect whether cookies are enabled through navigator.cookieEnabled

• Set cookies document.cookie = 'key=value';

• Get cookie document.cookie;

• Delete cookie document.cookie = "key=value;max-age=0";

• Set max-age storage perioddocument.cookie = "key=value;max-age=1000"; // 1000 seconds

• Set expires storage period

var timestamp = (new Date()).getTime() + 10000;var expires = new Date(timestamp).toGMTString();
//或toUTCStringdocument.cookie = "key=value;expires="+expires;

• Get specific cookie value

function getCookie(name) {
    var name = name + "=";    
    var ary = document.cookie.split(';');    
    for(var i = 0; i < ary.length; i++){        
    var c = ary[i];        
    while (c.charAt(0) == &#39; &#39;){
          c = c.substring(1);
        }        
        if (c.indexOf(name) != -1){          
        return c.substring(name.length, c.length);
        }
    }    return "";
}

Web Storage

Web Storage is divided into two types
localStorage and sessionStorage
The difference is:

• localStorage stores permanent data unless manually deleted

• sessionStorage stores temporary data and will disappear when the window is closed

Easy to use

Web Storage can only store string data
I think they can be understood as JSON
The usage methods are similar, taking localStorage as an example

localStorage.name = 'payen';
localStorage.info = JSON.stringify({name: 'payen', age: 20});
console.log(localStorage.name);
console.log(JSON.parse(localStorage.info));

The name of the data to be stored is the attribute name of localStorage
Ordinary strings can be stored normally That’s it
Object data can be converted to string format using JSON.stringify()
When used, JSON.parse() can be used to convert it back to object format
(If the object is stored directly, it will Forced to be converted into a string "[object Object]")

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To delete the data, just delete it

delete localStorage.name;delete localStorage.info;

If you do not delete it, the data in localStorage will always exist for you. The browser

API

localStorage and sessionStorage also provide a simple API
Similar to a client database
(APIs are the same)
Commonly used There are the following:

• Save data setItem(key, value)

• Read data getItem(key)

• Delete a single data removeItem(key)

• Clear all data clearItem()

• Get the data index key(index)

Example

Through this, we can write a simple address book

<p id="container">
    <br>
    <label for="username">姓名：</label>
    <input type="text" id="username" name="username">
    <br>
    <label for="mobilephone">手机：</label>
    <input type="text" id="mobilephone" name="mobilephone">
    <br><br>
    <input type="button" onclick="add()" id="add" value="增加联系人">
    <br><br>
    <hr>
    <label for="search">输入姓名：</label>
    <input type="text" id="search" name="search">
    <br><br>
    <input type="button" onclick="find()" id="find" value="查找手机号">
    <p id="result"><br></p></p>

#container {    
border: 2px solid gray;    
width: 320px;    
text-align:center;}

##It is implemented in JavaScript These two functions

var user = document.getElementById('username'),
    phone = document.getElementById('mobilephone'),
    search = document.getElementById('search'),
    result = document.getElementById('result');var add = function(){
    var u = user.value,
        p = phone.value,
        l = localStorage.length;    if(u !== '' && p !== ''){
        localStorage.setItem(u, p);
        user.value = '';
        phone.value = '';
        alert('添加成功');
    }
};var find = function(){
    var s = search.value,
        r = localStorage.getItem(s);    if(s !== '' && r){
        result.innerHTML = r;
    }
};

Enter the name and mobile phone number to add a contact

Then enter the contact name below and we can find the mobile phone number

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Of course this address book is very simple

You can also add it to display all the information in the address book
Delete contact function, etc.

Cookies and Web Storage Difference

Finally let’s talk about the difference between Html5’s Web Storage and Html4’s cookie

FeaturesCookieWeb StorageLife cycle is generally generated by the server and sets the time; generated by the browser, it is closed by default and the browser failslocal : Save permanently if not cleared; session: Close the page or the browser is invalidData size4KBOfficial recommendation 5MBCommunicationCarried in the HTTP header (excessive use may cause performance problems)Only stored in the browser, does not participate in communicationUsingThe native interface is not friendly and needs to be encapsulated manuallyThe native interface is friendly The above is the HTML5 client data storage Web Storage—localStorage and sessionStorage content. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!