Question

我有一个程序：

$(document).ready(function() {

   this.name = "John";
   var someFunc = function()
   {
     return this.name;
   }
});

根据我的理解，＆＃39; 这个＆＃39;在someFunc中是＆＃34;窗口＆＃34;因为它不包含在任何对象中。

我的问题是为什么＆＃39; this＆＃39;是＆＃39; HtmlDocument＆＃39;在$(document).ready(function() { alert(this) }？

由于someFunc位于$(document).ready函数之下，为什么它的价值不能是＆＃39; HtmlDocument＆＃39;还有？究竟发生在幕后的是什么导致了这种情况在不同情况下的价值不同？

Answer 1

阅读this（https://remysharp.com/2007/04/12/jquerys-this-demystified），例如在java脚本中简要概述“this”：

Answer 2

变量public function destroy(Request $request) { $ids = $request->input('deletecolor'); // Instead of raw SQL, you can use the query builder to make your life a bit easier $affected = DB::table('vehicle_color')->whereIn('id', $ids)->delete(); //echo $affected==1?"Successfully Deleted":"Delete Fail"; }在JavaScript中有一个范围概念，其值取决于您访问它的位置，我尝试用示例解释一下，请参阅以下代码段：

＆＃13;

this

＆＃13;

$("#document").ready(function() {
  console.log("HERE 'this' references to its owner object \"HTMLDocument\"");
  console.log(this.toString());
  jsFunction();
  $("#test").jqueryFunction();
  console.log("You could call jsFunction on window:");
  window.jsFunction();
  console.log("But you can't call jqueryFunction on window:");
  try{
    window.jqueryFunction();
  }catch(err){console.log("error");}
  console.log("Neither you could call jsFunction on \"div test\":");
  try{
    $("#test").jsFunction();
  }catch(err){console.log("error");}
  
  //Inner functions
  console.log("The same thing applies to inner functions");
  var innerFunc = function(){
    console.log(this.toString());
    
    var moreInnerFunc = function(){
      console.log(this.toString());
    }
    moreInnerFunc();
  }
  innerFunc();
  
  (function(){
    console.log("Immediately-Invoked Function Expression (IIFE)");
    console.log(this.toString());
  })();
  
  var extDeclared = externallyDeclared;
  extDeclared();
  $("#document").extDeclared();
});

function jsFunction(){
  console.log("HERE 'this' references to its owner \"window\"");
  console.log(this.toString());
}

(function( $ ){
 $.fn.jqueryFunction = function() {
    console.log("HERE 'this' references to its owner \"div test\"");
    console.log($(this).prop("id"));
 }; 
})( jQuery );

function externallyDeclared(){
  console.log("externallyDeclared may be window or its other owner");
  console.log(this.toString());
}

(function( $ ){
 $.fn.extDeclared = externallyDeclared;
})( jQuery );

＆＃13;

正如您所看到的，<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <div id="test" />始终引用其所有者＆＃34;对象，所以当你在任何类型的对象之外声明一个函数时，它的所有者是this对象，否则它引用定义函数的对象。

总结：

window

我希望我很清楚，再见。

这个＆＃39;的价值在函数内部

2 个答案: