setItem() 作为 Storage 接口的方法，接受一个键名和值作为参数，将会把键名添加到存储中，如果键名已存在，则更新其对应的值。
语法
storage.setItem(keyName, keyValue);
参数
返回值
无。
示例
下面的函数在本地存储中创建三个数据项（data items）。
function populateStorage() {
localStorage.setItem('bgcolor', 'red');
localStorage.setItem('font', 'Helvetica');
localStorage.setItem('image', 'myCat.png');
}
备注：一个实际的例子 Web Storage Demo。
规范
| Specification | Status | Comment |
|---|---|---|
| Unknown setItem() |
Unknown |
浏览器兼容性
We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
|---|---|---|---|---|---|
| localStorage | 4 | 3.5 | 8 | 10.50 | 4 |
| sessionStorage | 5 | 2 | 8 | 10.50 | 4 |
| Feature | Android | Firefox Mobile (Gecko) | IE Phone | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|
| Basic support | 2.1 | ? | 8 | 11 | iOS 3.2 |
各浏览器支持的 localStorage 和 sessionStorage 大小上限不同。测试页面 detailed rundown of all the storage capacities for various browsers。
Note: since iOS 5.1, Safari Mobile stores localStorage data in the cache folder, which is subject to occasional clean up, at the behest of the OS, typically if space is short.