that, self or me — which one to prefer in JavaScript?
While coding JavaScript sometimes you store the reference of object this
in a local variable for different purposes (to set proper scope, to help code obf开发者_Python百科uscators, etc.). There are coders who prefer aliasing this
to that
to make it obvious its intention. Other guys use self
since it's pointing to the object itself. I even saw source codes where me
held the reference and it still makes sense. Certainly there are other ones.
Which one should I prefer? Is there a convention on which to use or is it only the matter of taste.
I, personally, use that
, but anything else that's clear is fine.
I wouldn't use self
because the global variable/window
-property self
already exists as a reference to window
. Although it's totally useless (so no-one is likely to care that you're shadowing it), it slightly increases the risk of silly errors going unnoticed:
var se1f= this; // misspelled (perniciously). or maybe you just forgot to write line
onclick= function() {
self.foo= 1; // whoops, just wrote to `window`!
};
whereas:
var that= this;
onclick= function() {
that.foo= 1; // error thrown
};
Slightly contrived, but JavaScript's so sloppy with letting errors slide you don't really want to make it any more so.
There's an orange in your apple basket there, this
has a very specific contextual meaning. The choice is really between self
and me
of those options. Between those...you choose, it doesn't matter either way only personal preference.
this
refers to the context your in, so it's not really an "option" without introducing a lot of confusion and easy to make errors. I see self
used much more than me
(in example code, frameworks, libraries, etc). It's just preference, but I agree self
is more attractive, not sure why...again just my preference.
Well personally I'm trying to get better at making the variable mean something a little more than "that thing I need later". Often you need those temporary variables in situations that get a little gnarly; there might be two or more layers of temporary this
stashes to keep track of.
Thus, for example in a jQuery setup, I might use something to note the element type that a temporary this
stash should hold:
$('form').each(function() {
var $form = $(this);
$form.find('input:checkbox').each(function() {
var $checkbox = $(this);
// ...
});
});
Using the "$" prefix on the variables is a nice way to keep track of whether the object has been "jQuery-ized" or not :-)
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