Obsolete
This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.
The Array.observe()
method was used for asynchronously observing changes to Arrays, similar to Object.observe()
for objects. It provided a stream of changes in order of occurrence. It's equivalent to Object.observe()
invoked with the accept type list ["add", "update", "delete", "splice"]
. However, this API has been deprecated and removed from Browsers. You can use the more general Proxy
object instead.
Syntax
Array.observe(arr, callback)
Parameters
arr
- The array to be observed.
callback
- The function called each time changes are made, with the following argument:
changes
- An array of objects each representing a change. The properties of these change objects are:
name
: The name of the property which was changed.object
: The changed array after the change was made.type
: A string indicating the type of change taking place. One of"add"
,"update"
,"delete"
, or"splice"
.oldValue
: Only for"update"
and"delete"
types. The value before the change.index
: Only for the"splice"
type. The index at which the change occurred.removed
: Only for the"splice"
type. An array of the removed elements.addedCount
: Only for the"splice"
type. The number of elements added.
Description
The callback
function is called each time a change is made to arr
, with an array of all changes in the order in which they occurred.
Changes done via Array methods, such as Array.prototype.pop()
will be reported as "splice"
changes. Index assignment changes which do not change the length of the array may be reported as "update"
changes.
Examples
Logging different change types
var arr = ['a', 'b', 'c']; Array.observe(arr, function(changes) { console.log(changes); }); arr[1] = 'B'; // [{type: 'update', object: <arr>, name: '1', oldValue: 'b'}] arr[3] = 'd'; // [{type: 'splice', object: <arr>, index: 3, removed: [], addedCount: 1}] arr.splice(1, 2, 'beta', 'gamma', 'delta'); // [{type: 'splice', object: <arr>, index: 1, removed: ['B', 'c'], addedCount: 3}]
Specifications
Strawman proposal specification.
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
observe | Chrome No support 36 — 52 | Edge No support No | Firefox No support No | IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Firefox Android No support No | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No |
Legend
- No support
- No support
- Non-standard. Expect poor cross-browser support.
- Non-standard. Expect poor cross-browser support.
- Deprecated. Not for use in new websites.
- Deprecated. Not for use in new websites.