Chrome中使用的变量$ x是什么？ [英] What is the variable $x used for in Chrome?

问题描述

几天前，我和一个朋友在Chrome浏览器中使用Javascript控制台（使用稍旧的版本，但是可以在OSX和Windows的最新稳定版本中重复），当我们为字符串分配一个字符串变量$ x。

  $ x =hello
  

但是当我们回显$ x的值时，我们会在控制台中获得以下代码：

  bound：function（xpath，context）
 {
 var doc =（context&& context.ownerDocument）|| inspectedWindow.document; 
 var result = doc.evaluate（xpath，context || doc，null，XPathResult.ANY_TYPE，null）; 
 switch（result.resultType）{
 case XPathResult.NUMBER_TYPE：
 return result.numberValue; 
 case XPathResult.STRING_TYPE：
 return result.stringValue; 
 case XPathResult.BOOLEAN_TYPE：
 return result.booleanValue; 
默认值：
 var nodes = []; 
 var node; 
 while（node = result.iterateNext（））
 nodes.push（node）; 
返回节点; 
 
 
 
 
 $ b我们在稳定版本的Safari中获得了类似的输出， Firefox浏览器。据我们所知，$ x变量没有附加到全局窗口对象。 
 
 
 
什么是$ x，它用于什么？ 
 
解决方案
这是一个XPath实用程序功能。从精美的Firebug手册：
 
 
   $ x（xpath）  
 
返回
 
 
并从 fine Chrome manual ： 
 $ b 
 
 
  $ x（xpath） 
 
返回与给定的XPath表达式匹配的DOM元素数组。
 
 
 
 
 
  $ x 函数不是JavaScript本身的一部分，它只是一个在控制台中可用的实用程序。如果您尝试在控制台外访问 $ x （ http： //jsfiddle.net/ambiguous/fsewU/ ），你会得到一个ReferenceError，除非你已经在某处定义了你自己的 $ x 。  
A few days ago a friend and I were playing around with the Javascript console in Chrome (using a slightly older version, but this can be repeated in the latest stable build on both OSX and windows) when we assigned a string to the variable $x.
$x = "hello"
but when we echo out the value of $x, we get given the following code in the console:
bound: function (xpath, context)
{
    var doc = (context && context.ownerDocument) || inspectedWindow.document;
    var result = doc.evaluate(xpath, context || doc, null, XPathResult.ANY_TYPE, null);
    switch (result.resultType) {
    case XPathResult.NUMBER_TYPE:
        return result.numberValue;
    case XPathResult.STRING_TYPE:
        return result.stringValue;
    case XPathResult.BOOLEAN_TYPE:
        return result.booleanValue;
    default:
        var nodes = [];
        var node;
        while (node = result.iterateNext())
            nodes.push(node);
        return nodes;
    }
}
We got a similar output in stable versions of Safari and Firefox. As far as we can tell, the $x variable is not attached to the global window object. 

What is $x, and what's it used for?
解决方案
That's an XPath utility function. From the fine Firebug manual:

  
$x(xpath)

  Returns an array of elements that match the given XPath expression.
And from the fine Chrome manual:

  
$x(xpath)

  Returns an array of DOM elements that match the given XPath expression.
The $x function isn't part of JavaScript itself, it is just a utility that's available in the console. If you try to access $x outside the console (http://jsfiddle.net/ambiguous/fsewU/), you'll get a ReferenceError unless, of course, you've defined your own $x somewhere.

                        
这篇关于Chrome中使用的变量$ x是什么？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！