具有多个表达式的JavaScript中的三元运算符？

Question

the_styles ? the_styles.appendTo('head'); the_styles=null : the_styles = $('.stylesheet').detach();

Obviously, this isn't valid. Notice the ";" between the appendTo() and the_styles=null . How do I write it on 1 line and still have multiple expressions like that?

Answer 1

Use the comma operator this way:

the_styles ? (the_styles.appendTo('head'), the_styles=null) : the_styles =  $('.stylesheet').detach();

Here's what the Mozilla Developer Center writes about the comma operator:

You can use the comma operator when you want to include multiple expressions in a location that requires a single expression. The most common usage of this operator is to supply multiple parameters in a for loop.

Read more here: https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Operators/Special_Operators/Comma_Operator

Answer 2

Who needs the ternary operator?

​the_styles = !the_styles && $('.stylesheet').detach()​​​​ ||
             the_styles.appendTo('head') && null;​

Had to switch the expressions around as otherwise the null value of the first expression will always force the second expression .detach() to be evaluated.

The only thing about clever code is that once you come back to it after a coffee break, it won't make any sense even to you. So this is much better:

if(the_styles) {
    the_styles.appendTo('head')
    the_styles = null;
}
else {
    the_styles = the_styles.detach('.stylesheet');
}

To me, even the above simplistic version doesn't make any sense. The what part is obvious, but why is it doing that?

Answer 3

the_styles ? (function() {the_styles.appendTo('head'); the_styles=null})() : <etc>

Just wrap the code block in (function() { and })() .

Now for the hard part: why would you want to do this? Perhaps there's a better solution!

Answer 4

我同意glowcoder，但如果你仍然想要它：

the_styles ? function(){ the_styles.appendTo('head'); the_styles=null;}() : the_styles = $('.stylesheet').detach();

Answer 5

the_styles ? the_styles.appendTo('head') : the_styles = $('.stylesheet').detach();

如果你覆盖它，你不需要取消它！

Answer 6

the_styles=the_styles || $('.stylesheet').detach(); the_styles.appendTo('head');