observe() configures the
MutationObserver callback to begin receiving notifications of changes to the DOM that match the given options. Depending on the configuration, the observer may watch a single
Node in the DOM tree, or that node and some or all of its descendant nodes.
To stop the
MutationObserver (so that none of its callbacks will be triggered any longer), call
Node(which may be an
Element) within the DOM tree to watch for changes, or to be the root of a subtree of nodes to be watched.
MutationObserverInitobject providing options that describe what DOM mutations should be reported to the observer's
MutationObserverInit.characterDataare all false).
false(indicating that attribute changes are not not to be monitored) but
false(indicating that character changes aren't to be tracked).
You can call
observe() multiple times on the same
MutationObserver to watch for changes to different parts of the DOM tree and/or different types of changes. There are some caveats to note:
observe()on a node that's already being observed by the same
MutationObserver, all existing observers are automatically removed from all targets being observed before the new observer is activated.
MutationObserveris not already in use on the target, then the existing observers are left alone and the new one is added.
Mutation observers are intended to let you be able to watch the desired set of nodes over time, even if the direct connections between those nodes are severed. If you begin watching a subtree of nodes, and a portion of that subtree is detached and moved elsewhere in the DOM, you continue to watch the detached segment of nodes, receiving the same callbacks as before the nodes were detached from the original subtree.
In other words, until you've been notified that nodes are being split off from your monitored subtree, you'll get notifications of changes to that split-off subtree and its nodes. This prevents you from missing changes that occur after the connection is severed and before you have a chance to specifically begin monitoring the moved node or subtree for changes.
This means that in theory if you keep track of the
MutationRecord objects describing the changes that occur, and , you should be able to "undo" the changes, rewinding the DOM back to its initial state.
The definition of 'MutationObserver.observe()' in that specification.
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