Local Storage using HTML5 can efficiently store browser-side data. 1. Basic operations include using setItem() to store data, getItem() to retrieve data, and when accessing objects, you need to use JSON.stringify() and JSON.parse() to convert it; 2. Use removeItem() to delete data, and use clear() to clear it; 3. It is suitable for saving non-sensitive information such as user preferences, pay attention to the 5MB storage upper limit, data persistence and homologous strategy; 4. It is recommended to check whether the browser supports Storage before use.
Using HTML5's local storage is actually quite simple. The key is to understand what it can do and how it can be used. Unlike cookies, every request is sent to the server, Local Storage is present in the browser and is suitable for saving some data that does not require frequent transmission.
1. Basic operations: Save and withdraw
The two most core methods of Local Storage are setItem() and getItem() , which are used to store and retrieve data respectively.
For example, you want to save the user's username:
localStorage.setItem('username', 'Tom');
Then want to display it on the page:
let name = localStorage.getItem('username'); console.log(name); // Output Tom
Note: Local Storage is a string type. If you want to save objects or arrays, remember to use JSON.stringify() first:
let user = { name: 'Tom', age: 25 };
localStorage.setItem('user', JSON.stringify(user)); When reading, you should also use JSON.parse() to restore it to an object:
let userData = JSON.parse(localStorage.getItem('user')); console.log(userData.name); // Output Tom
2. Delete and clear data
Sometimes you may need to delete a key-value pair or simply clear it all.
- Delete a single key-value pair:
localStorage.removeItem('username');
- Clear all data:
localStorage.clear();
These two methods are not used much but are important, especially when users log out or reset settings.
3. Use scenarios and precautions
Local Storage is suitable for saving user preferences, form drafts, theme settings, etc. that are insensitive but want to be persistent. For example, remember the theme color the user chose last time, or save shopping cart information (but you should pay attention to safety and do not place sensitive data).
A few things to note:
- The storage size is usually capped at about 5MB, and there are slight differences between different browsers.
- Data will not expire unless manually cleared.
- Same-origin policy restrictions, that is, only pages under the same domain name can access the same Local Storage.
- Cross-domain access is not supported, so don't expect one website to read data stored on another website.
4. Check whether Local Storage is supported
Although most modern browsers now support Local Storage, it is recommended to do a test for safety reasons:
if (typeof(Storage) !== "undefined") {
// Support Local Storage
} else {
// Not supported, consider using cookies or other methods instead}This can avoid errors from older browsers.
Basically, that's all, it doesn't seem complicated, but there are several details that are easy to ignore when used, such as type conversion, cross-domain issues, storage capacity, etc. Just pay attention to these points, Local Storage can save you a lot of trouble.
The above is the detailed content of How to use HTML5 local storage?. For more information, please follow other related articles on the PHP Chinese website!
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