How to operate JQuery elements

This time I will show you how to operate JQuery elements and what are the precautions for operating JQuery elements. The following is a practical case, let's take a look.

First, let’s take a look at how to find the desired node in jquery.

Step one: sizzle selector

"Find" (or select) HTML elements based on the element's id, class, type, attribute, attribute value, etc., simple It is said to be based on css selectors, in addition to some specific selectors.

Step 2: Query ancestors

parent()

Returns the direct parent element of the selected element. This method will only go up one level. DOM tree traversal

parents()

Optional parameters can be used to filter the search for parent elements
Returns all ancestor elements of the selected element, all the way up to the root of the document Element

parentsUntil()

Returns all ancestor elements between two given elements. The following is an example:

$(document).ready(function(){
  //会返回span开始到p为止的祖先元素
  $("span").parentsUntil("p");
});

Step 3: Query Descendants

children()

You can use optional parameters to filter the search for child elements

Returns all direct child elements of the selected element. This method only The DOM tree will be traversed to the next level

find()

You can use optional parameters to filter the search for elements

Returns the descendant elements of the selected element. All the way down to the last descendant

Step 4: Query siblings

siblings()

Return all sibling elements of the selected element

next()

Returns the next sibling element of the selected element

nextAll()

Returns all sibling elements after the selected element

nextUntil()

Returns all following sibling elements between the two given arguments

$(document).ready(function(){
  //返回介于 <h2>与<h6>元素之间的所有同胞元素
  $("h2").nextUntil("h6");
});

prev(), prevAll() and prevUntil()

The prev(), prevAll() and prevUntil() methods work similarly to the above methods, except in the opposite direction: they return the previous sibling elements (traversing along the previous sibling elements in the DOM tree, and Not after element traversal).

Step 5: Add filtering when querying

first()

Return the first element among the selected elements

last()

Returns the last element among the selected elements

eq()

Returns the element with the specified index number among the selected elements. This is easy to understand. , an example is: $(element[flag]) has the same result as element.eq(flag)

filter()

Filters the query results, similar to not() below, but has the opposite effect

not()

Return all elements that do not match the standard

$(document).ready(function(){
  //返回不带有类名"target"的所有p元素
  $("p").not(".target");
});

After the element is found, we then need to operate on the found node according to the requirements.

Step 6: text(), html(), val() and attr()

text(), html(), val() and attr (), has a callback function. The callback function takes two parameters: the index of the current element in the selected element list, and the original (old) value. Then return the string you wish to use as the function's new value

1.text() - Sets or returns the text content of the selected element

2.html() - Sets or returns the selected element The content of the element (including HTML tags)

3.val() - Sets or returns the value of a form field

4.attr() - Sets or returns the value of an attribute

$("#btn1").click(function(){
  $("#test1").text(function(i,origText){
  
    return "旧文本: " + origText + " 新文本: index: " + i;
    
  });
  
});

Step 7: Add elements

append() - Insert content at the internal end of the selected element

prepend() - Insert content at the internal beginning of the selected element Content

after() - Insert content after the selected element

before() - Insert content before the selected element

Step 8: Delete the element

remove() accepts one parameter, allowing you to filter deleted elements. empty() cannot

remove() - delete the selected element (and its sub-elements) )

empty() - removes child elements from the selected elements

//等同于$("p.target").remove();
$("p").remove(".target");

第九步：替换元素

replaceAll()和replaceWith()功能类似，但是目标和源相反

replaceWith() - 用提供的内容替换集合中所有匹配的元素并且返回被删除元素的集合

replaceAll() - 用集合的匹配元素替换每个目标元素

第十步：class操作

addClass() - 向被选元素添加一个或多个类

removeClass() - 从被选元素删除一个或多个类

toggleClass() - 对被选元素进行添加/删除类的切换操作

hasClass() - 判断一个元素是否存在该class

第十一步：css()方法

设置或返回被选元素的一个或多个样式属性

css("propertyname"); - 返回propertyname属性的值

css("propertyname","value"); - 设置propertyname属性的值

css({"propertyname":"value","propertyname":"value",...}); - 设置多个值

第十二步：元素尺寸

width() 方法设置或返回元素的宽度（不包括内边距、边框或外边距）

height() 方法设置或返回元素的高度（不包括内边距、边框或外边距）

innerWidth() 方法返回元素的宽度（包括内边距）

innerHeight() 方法返回元素的高度（包括内边距）

outerWidth() 方法返回元素的宽度（包括内边距和边框）

outerHeight() 方法返回元素的高度（包括内边距和边框）

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