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JQuery, selectors/filters/performance optimization

炎欲天舞
Release: 2017-08-04 14:50:10
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  1. Browser introduction:

    1. The jquery object is an array-like object. The array-like object has length and can be passed Index access, if the array-like object is not added manually, the methods of the array object are not available.

    2. The length of an array will automatically grow when adding elements, but a class array will not.

    3. Class arrays can be converted into arrays through the slice method:


##

Array.prototype.slice.call(a);
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  1. JQuery basic selector:

    1. ID selector

    2. Class selector

    3. Descendant selector

    4. Attribute selector

    5. a[href!="http://www.baidu.com"], a new method in jquery, selects all elements that are not equal to Baidu URL.

  1. JQuery Filter/Filter:

  • lang(language) :Select elements in the specified language

  • not(selector) :Select all elements that are not the specified elements

  • root                                                                                                                                                                                                                                                  Contains OPACITY, does not include HIDDEN elements, excluding elements that are not displayed in the position

  • Visible: Just opposite to Hidden

  • ## Header :Select the title element
  • animated :Select all elements that are performing animation effects
  • ##:empty :Select the content Empty elements

  • : contains(text) : Select elements to filter text

: has(selector) : For example, select p:has (span)
  • :parent :Select the parent element
  • :first-child

  • :last-child

  • ##first-of-type : Select the first one with the same type: li:first-of-type
  • last-of-type

  • nth-child() : Counting from 1

  • nth-last-child()

  • nth-of-type()

  • ##nth-last-of-type()

  • only-child

  • only-of-type

  • ##:checked : Select the selected

  • :disabled : Select and disable

  • :enabled : All except disabled ones can be selected

    : focus : generally not used directly, wait until the form is loaded before using
  • : button : not only selects the button, but also selects the type of button
  • :checkbox :Select all multi-select boxes
  • :file :Select the file input box
  • :image :Select the type of image Element
  • :input : Select all form elements
  • :password
  • :radio : Select the radio button
  • :reset :The selected type is reset,
  • :selected :Select all selected states
  • :submit : The selected type is submit, and some browsers will also select button
  • :text : The selected type is text, and ## with no type set will also be selected.
  • #:first

  • :last

  • :even

:odd
  • :eq(n) : equal to n
  • ##:gt(n) : greater than n

  • :lt(n) : less than n

  • Position filter:
  • Form Filter
  • Child Element Filter
  • Content Filter
  1. ## Other filters

  2. Custom selector

  1. Performance optimization of JQuery selector:

    1. Try to use selectors available in CSS

    2. Avoid over-constraints

    3. Try to start with ID

    4. Let the selector have more features on the right side

    5. Avoid using global selectors

    6. Cache selector results

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