watch-dom —— Monitor DOM changes

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Description

Monitor changes to nodes on a specified DOM tree or changes to the size of element box models and allow processing of changes.

Getting Started

Install dependencies

npm i @cailiao/watch-dom

Import

the patch function

import { patch } from '@cailiao/watch-dom'

// Choosing to execute the patch function at the right time will create two prototype methods $watch and $watchBox on the global class Element.
patch()

// Or import only the specified methods as needed, watch is equivalent to the $watch method on the prototype, and watchBox is equivalent to the $watchBox method on the prototype.
import { watch, watchBox } from '@cailiao/watch-dom'

Usage

• patch function

// Monitor changes to child nodes on the DOM tree. targetElement is an instance of any built-in Element class, i.e., a DOM element.
const unwatch = targetElement.$watch(record => { console.log(record) }, { subtree: true, childList: true })
// Cancel monitoring
unwatch()


// Monitor changes to the size of element box models. targetElement is an instance of any built-in Element class, i.e., a DOM element.
const unwatch = targetElement.$watchBox(record => { console.log(record) }, { subtree: true, childList: true })
// Cancel monitoring
unwatch()
// Pause monitoring
unwatch.pause()
// Resume monitoring
unwatch.resume()

• import only needed

// Monitor changes to child nodes on the DOM tree. targetElement is an instance of any built-in Element class, i.e., a DOM element.
const unwatch = watch(targetElement, record => { console.log(record) }, { subtree: true, childList: true })
// Cancel monitoring
unwatch()


// Monitor changes to the size of element box models. targetElement is an instance of any built-in Element class, i.e., a DOM element.
const unwatch = watchBox(targetElement, record => { console.log(record) }, { subtree: true, childList: true })
// Cancel monitoring
unwatch()
// Pause monitoring
unwatch.pause()
// Resume monitoring
unwatch.resume()

Explanation

The patch() method inserts two methods, $watch and $watchBox, on the prototype of Element. The directly imported watch is equivalent to the $watch method on the prototype, and watchBox is equivalent to the $watchBox method on the prototype, with only slight differences in the parameters passed in.

$watch Function

Parameters

• callback: Required. Function type. Pass in one parameter,

  • record is an array of MutationRecord. It contains information about the modification of the DOM.

  • observer: A reference to ResizeObserver itself.

• options: Required. Object type. It is the options parameter of MutationObserver.observe(),

  Options are as follows:

  • subtree Optional

    Set to true to extend monitoring to the entire subtree of nodes rooted at target. All of the other properties are then extended to all of the nodes in the subtree instead of applying solely to the target node. The default value is false.

  • childList Optional

    Set to true to monitor the target node (and, if subtree is true, its descendants) for the addition of new child nodes or removal of existing child nodes. The default value is false.

  • attributes Optional

    Set to true to watch for changes to the value of attributes on the node or nodes being monitored. The default value is true if either of attributeFilter or attributeOldValue is specified, otherwise the default value is false.

  • attributeFilter Optional

    An array of specific attribute names to be monitored. If this property isn't included, changes to all attributes cause mutation notifications.

  • attributeOldValue Optional

    Set to true to record the previous value of any attribute that changes when monitoring the node or nodes for attribute changes; See Monitoring attribute values for details on watching for attribute changes and value recording. The default value is false.

  • characterData Optional

    Set to true to monitor the specified target node (and, if subtree is true, its descendants) for changes to the character data contained within the node or nodes. The default value is true if characterDataOldValue is specified, otherwise the default value is false.

  • characterDataOldValue Optional

    Set to true to record the previous value of a node's text whenever the text changes on nodes being monitored. The default value is false.

returns: Function

Returns a function to cancel the monitor.

$watchBox Function

Parameters

• callback: Required. Function type. Pass in two parameters,

  • record is an array of ResizeObserverEntry. It contains information about the modified size of elements.

  • observer: A reference to ResizeObserver itself.

• options: Optional. Object type. It is the options parameter of ResizeObserver.observe(),The properties of options are as follows:

  • box Sets which box model the observer will observe changes to. Possible values are:

    • content-box (the default)

      Size of the content area as defined in CSS.

    • border-box

      Size of the box border area as defined in CSS.

    • device-pixel-content-box

      The size of the content area as defined in CSS, in device pixels, before applying any CSS transforms on the element or its ancestors.

returns: Function

Returns a function to cancel the monitor.

• pause：Function type, causes the current monitor to pause monitoring.

• resume：Function type, resumes monitoring to the current monitor. Should be called only after pause() has been called.

watch Function

Parameters

• target：Required. HTMLAllCollection type.

• callback: Required. Function type. Pass in one parameter,

  • record is an array of MutationRecord. It contains information about the modification of the DOM.

  • observer: A reference to ResizeObserver itself.

• options: Required. Object type. It is the options parameter of MutationObserver.observe(),

  • Options are as follows:

  • subtree Optional

    Set to true to extend monitoring to the entire subtree of nodes rooted at target. All of the other properties are then extended to all of the nodes in the subtree instead of applying solely to the target node. The default value is false.

  • childList Optional

    Set to true to monitor the target node (and, if subtree is true, its descendants) for the addition of new child nodes or removal of existing child nodes. The default value is false.

  • attributes Optional

    Set to true to watch for changes to the value of attributes on the node or nodes being monitored. The default value is true if either of attributeFilter or attributeOldValue is specified, otherwise the default value is false.

  • attributeFilter Optional

    An array of specific attribute names to be monitored. If this property isn't included, changes to all attributes cause mutation notifications.

  • attributeOldValue Optional

    Set to true to record the previous value of any attribute that changes when monitoring the node or nodes for attribute changes; See Monitoring attribute values for details on watching for attribute changes and value recording. The default value is false.

  • characterData Optional

    Set to true to monitor the specified target node (and, if subtree is true, its descendants) for changes to the character data contained within the node or nodes. The default value is true if characterDataOldValue is specified, otherwise the default value is false.

  • characterDataOldValue Optional

    Set to true to record the previous value of a node's text whenever the text changes on nodes being monitored. The default value is false.

returns: Function

Returns a function to cancel the monitor.

watchBox Function

Parameters

• target：Required. HTMLAllCollection type.

• callback: Required. Function type. Pass in two parameters,

  • record is an array of ResizeObserverEntry. It contains information about the modified size of elements.

  • observer: A reference to ResizeObserver itself.

• options: Optional. Object type. It is the options parameter of ResizeObserver.observe(),The properties of options are as follows:

  • box Sets which box model the observer will observe changes to. Possible values are:

    • content-box (the default)

      Size of the content area as defined in CSS.

    • border-box

      Size of the box border area as defined in CSS.

    • device-pixel-content-box

      The size of the content area as defined in CSS, in device pixels, before applying any CSS transforms on the element or its ancestors.

returns: Function

Returns a function to cancel the monitor.

• pause：Function type, causes the current monitor to pause monitoring.

• resume：Function type, resumes monitoring to the current monitor. Should be called only after pause() has been called.

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