In this question, the following code is used -
在这个问题中，使用以下代码 -
var parent = $("#jcontent");
var button1 = $(".button1", parent) ;
to select a button of class button1 within the parent of id jcontent.
在id jcontent的父级中选择类button1的按钮。
Why does this work? How does passing a jQuery object as a parameter to a jQuery selector tell it to select within that object? Can someone link to the docs which explain this function?
为什么这样做？如何将jQuery对象作为参数传递给jQuery选择器告诉它在该对象中进行选择？有人可以链接到解释此功能的文档吗？
2 个解决方案
#1
6
It's the context parameter for the core method call.
它是核心方法调用的上下文参数。
The parameter is described as:
该参数描述为：
A DOM Element, Document, or jQuery to use as context
用作上下文的DOM元素，文档或jQuery
And then there's a section labelled "Selector Context," which starts with:
然后有一个标记为“选择器上下文”的部分，它以：
By default, selectors perform their searches within the DOM starting at the document root. However, an alternate context can be given for the search by using the optional second parameter to the $() function.
默认情况下，选择器在DOM中从文档根开始执行搜索。但是，通过使用$（）函数的可选第二个参数，可以为搜索提供备用上下文。
#2
5
The second parameter is the selector context: the DOM element, document, or jQuery object inside which the selector is matched. In the absence of this parameter, document root is assumed.
第二个参数是选择器上下文：选择器匹配的DOM元素，文档或jQuery对象。如果没有此参数，则假定文档根。
The following statement:
以下声明：
var button1 = $(".button1", parent); // parent = $("#jcontent")
is same as writing **:
与写**相同：
var button1 = parent.find(".button1"); // parent = $("#jcontent")
and (in this case) produces results identical to this:
和（在这种情况下）产生与此相同的结果：
var button1 = $("#jcontent .button1");
** as mentioned here:
**如上所述：
Internally, selector context is implemented with the .find() method, so $('span', this) is equivalent to $(this).find('span').
在内部，选择器上下文是使用.find（）方法实现的，因此$（'span'，this）等价于$（this）.find（'span'）。
#1
6
It's the context parameter for the core method call.
它是核心方法调用的上下文参数。
The parameter is described as:
该参数描述为：
A DOM Element, Document, or jQuery to use as context
用作上下文的DOM元素，文档或jQuery
And then there's a section labelled "Selector Context," which starts with:
然后有一个标记为“选择器上下文”的部分，它以：
By default, selectors perform their searches within the DOM starting at the document root. However, an alternate context can be given for the search by using the optional second parameter to the $() function.
默认情况下，选择器在DOM中从文档根开始执行搜索。但是，通过使用$（）函数的可选第二个参数，可以为搜索提供备用上下文。
#2
5
The second parameter is the selector context: the DOM element, document, or jQuery object inside which the selector is matched. In the absence of this parameter, document root is assumed.
第二个参数是选择器上下文：选择器匹配的DOM元素，文档或jQuery对象。如果没有此参数，则假定文档根。
The following statement:
以下声明：
var button1 = $(".button1", parent); // parent = $("#jcontent")
is same as writing **:
与写**相同：
var button1 = parent.find(".button1"); // parent = $("#jcontent")
and (in this case) produces results identical to this:
和（在这种情况下）产生与此相同的结果：
var button1 = $("#jcontent .button1");
** as mentioned here:
**如上所述：
Internally, selector context is implemented with the .find() method, so $('span', this) is equivalent to $(this).find('span').
在内部，选择器上下文是使用.find（）方法实现的，因此$（'span'，this）等价于$（this）.find（'span'）。