是'这个'总是为功能定义？ [英] is 'this' always defined for functions?
问题描述
http://www.frostjedi.com/terra /scripts/demo/this.html
''this''被定义为，据我所知，对于事件处理程序，但为什么是
$ b它定义了$ b，这里？
这里是代码：
<！DOCTYPE html PUBLIC" - // W3C // DTD XHTML 1.0 Strict // EN"
" http：//www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
< html xmlns =" http：//www.w3.org/1999/xhtml" XML：朗= QUOT;恩" >
< head>
< title> this< / title>
< / head>
< body>
< script type =" text / javascript">
（function（）{
if（this）{
alert（test exists）;
} else {
alert（" test doesn' 不存在）;
}
}）（）;
< / script>
< ; / body>
< / html>
http://www.frostjedi.com/terra/scripts/demo/this.html
''this'' is defined, as I understand it, for event handlers, but why is
it defined, here?
Here''s the code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" >
<head>
<title>this</title>
</head>
<body>
<script type="text/javascript">
(function() {
if (this) {
alert("test exists");
} else {
alert("test doesn''t exist");
}
})();
</script>
</body>
</html>
推荐答案
yawnmoth< te ******* @ yahoo.comwrites：
yawnmoth <te*******@yahoo.comwrites:
http://www.frostjedi.com/terra/scripts/demo/this.html
''这个''已定义，据我了解，对于事件处理程序，但为什么它定义了
，这里？
这里是代码：
<！DOCTYPE html PUBLIC" - // W3C // DTD XHTML 1.0 Strict // EN"
" http：//www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
< html xmlns =" http ：//www.w3.org/1999/xhtml" XML：朗= QUOT;恩" >
< head>
< title> this< / title>
< / head>
< body>
< script type =" text / javascript">
（function（）{
if（this）{
alert（test exists）;
} else {
alert（" test doesn' 不存在）;
}
}）（）;
< / script>
< ; / body>
< / html>
http://www.frostjedi.com/terra/scripts/demo/this.html
''this'' is defined, as I understand it, for event handlers, but why is
it defined, here?
Here''s the code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" >
<head>
<title>this</title>
</head>
<body>
<script type="text/javascript">
(function() {
if (this) {
alert("test exists");
} else {
alert("test doesn''t exist");
}
})();
</script>
</body>
</html>
" this"表示方法调用的对象。简而言之，无论什么时候它都没有引用更具体的东西，它指的是全局的
对象（窗口对象，忽略了一些细节）。
在特定对象的方法调用中，this指的是
调用的对象（在这方面，DOM事件就像方法调用一样）。
函数bla（）{
//用this做一些事情
}
bla（）//对全局对象采取行动
var foo = {bar：bla}
foo.bla（）//对foo对象采取行动
var zee = {};
foo.bla.call（z）//作用于zee对象
-
Joost Diepenmaat |博客： http://joost.zeekat.nl/ |工作： http://zeekat.nl/
"this" means the object of a method call. in short, whenever it
doens''t refer to anything more specific, it refers to the global
object (the "window" object, ignoring some details).
In method calls on a specific object, "this" refers to the object of
the call (and DOM events act like method calls in that respect).
function bla() {
// do something with "this"
}
bla() // act on the global object
var foo = { bar: bla }
foo.bla() // act on the foo object
var zee = {};
foo.bla.call(z) // act on the zee object
--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/
Joost Diepenmaat< jo *** @ zeekat.nlwrites：
Joost Diepenmaat <jo***@zeekat.nlwrites:
var zee = {};
foo.bla.call（z）//对zee对象执行操作
var zee = {};
foo.bla.call(z) // act on the zee object
应该是
foo。 bla.call（zee）//作用于zee对象
-
Joost Diepenmaat |博客： http://joost.zeekat.nl/ |工作： http://zeekat.nl/
that should have been
foo.bla.call(zee) // act on the zee object
--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/
8月26日下午4：20 *，Joost Diepenmaat< jo ... @ zeekat.nlwrote：
On Aug 26, 4:20*pm, Joost Diepenmaat <jo...@zeekat.nlwrote:
Joost Diepenmaat< jo .. 。@ zeekat.nlwrites：
Joost Diepenmaat <jo...@zeekat.nlwrites:
var zee = {};
var zee = {};
foo.bla.call（z）//对zee对象执行操作
foo.bla.call(z) // act on the zee object
应该是
foo.bla.call（zee）//对zee对象执行操作
that should have been
foo.bla.call(zee) // act on the zee object
谢谢 - 我很感激！
Thanks - I appreciate it!
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