This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.
The has() method of the CacheStorage interface returns a Promise that resolves to true if a Cache object matches the cacheName.
Syntax
caches.has(cacheName).then(function(true) {
// your cache exists!
});
Returns
a Promise that resolves to true if the cache exists or false if not.
Parameters
- cacheName
- A
DOMStringrepresenting the name of theCacheobject you are looking for in theCacheStorage.
Examples
The following example first checks whether a cache called 'v1' exists. If so, we add a list of assets to it. If not (meaning the has() promise would reject) then we run some kind of cache set-up function.
caches.has('v1').then(function(hasCache) {
if (!hasCache) {
someCacheSetupfunction();
} else {
caches.open('v1').then(function(cache) {
return cache.addAll(myAssets);
});
}
}).catch(function() {
// Handle exception here.
});;
Specifications
| Specification | Status | Comment |
|---|---|---|
| Service Workers The definition of 'CacheStorage' in that specification. |
Working Draft | Initial definition. |
Browser compatibility
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|
| Basic support | 40.0 | 44 (44)[1] | No support | ? | No support |
| Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
|---|---|---|---|---|---|---|---|
| Basic support | No support | No support | 44.0 (44) | (Yes) | (Yes) | (Yes) | 40.0 |
[1] Service workers (and Push) have been disabled in the Firefox 45 & 52 Extended Support Releases (ESR.)