Javascript 如何在 jQuery 中进行 if-then 速记？这些可以链接吗？
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How to do a shorthand if-then in jQuery? Are these chainable?
提问by frequent
Actually two questions:
其实两个问题：
I like the shorthand IF-ELSEin jQuerylike so:
我喜欢jQuery 中的速记IF-ELSE，如下所示：
var some == true ? "it's true" : "it's false";
Is there a corresponding IF-THEN, because this:
是否有相应的IF-THEN，因为：
var some == true ? "it's true"
doesn't seem to work.
似乎不起作用。
Also, would something like this be chainable in regular jQuery? Like so:
另外，像这样的东西可以在常规 jQuery 中链接吗？像这样：
some.addClass("hello")
.find(".other").css("width","100px").end()
// chained if
.hasClass("one") ? some.css("border","1px solid red")
.removeClass("hello")
Now that would be nice, wouldn't it? Is this possible?
现在那会很好，不是吗？这可能吗？
采纳答案by ipr101
There are a couple of plug-ins that allow you to chain iflogic in jQuery -
有几个插件可以让你if在 jQuery 中链接逻辑 -
http://outwestmedia.com/jquery-plugins/conditional/
http://outwestmedia.com/jquery-plugins/conditional/
$('div')
.If('hasClass', 'myClass')
.css('color', 'red')
.Else('hasClass', 'anotherClass')
.css('color', 'green')
.Else()
.css('color', 'blue');
http://benalman.com/projects/jquery-iff-plugin/
http://benalman.com/projects/jquery-iff-plugin/
function my_test( x ) {
return x === 'bar';
};
$('div')
.append( '1' )
.iff( my_test, 'foo' )
.append( '2' )
.end()
.append( '3' );
回答by GillesC
That will do (assignment uses a single =, two is for conditions), but if the first one is true, like you posted, some will ALWAYS be true.
那会做（赋值使用单个 =，两个用于条件），但如果第一个是真的，就像你发布的那样，有些永远是真的。
var some = true || "it's true";
And no, your example wouldn't be chainable, but you could replace your hasClass by filter('.one')which will continue the chain if there are elements containing the class one:
不，您的示例将无法链接，但是您可以替换您的 hasClass，filter('.one')如果有包含第一个类的元素，它将继续链：
some.addClass("hello")
.find(".other").css("width","100px").end()
.filter('.one').css("border","1px solid red")
.removeClass("hello")
回答by adeneo
The shorthand IF/ELSE you are reffering to is called a ternary operator, and it's not chainable in the same way as a IF/ELSE statements, nor is it chainable as a jQuery method, and there are some limits to it's use, you can however place one inside the other, like so:
您所指的速记 IF/ELSE 称为三元运算符，它不像 IF/ELSE 语句那样可链接，也不能作为 jQuery 方法链接，并且它的使用有一些限制，您可以但是将一个放在另一个里面，如下所示：
some == true ? someMore == true ? "it's true" : "it's false" : "it's false";
You can also do:
你也可以这样做：
some == true ? "it's true" : null;
//or
some == true ? "it's true" : undefined;
This returns something, so usually it's used like so:
这会返回一些东西，所以通常它是这样使用的：
var some = someVar==true ? "it's true" : "it's false";
In other words you can do:
换句话说，你可以这样做：
var some = $(some).length ?
$(some).is('.one') ?
some //some exists and have the class .one
:
return someOtherVar or function //some does not have the class .one
:
undefined //some does not have a length
;
You could also do something similar to this, and there are many different ways to use a ternary:
你也可以做类似的事情，有很多不同的方法可以使用三元：
$(div)[somevar==true ? fadeIn : fadeOut](300);
Other than that, when having a lot of stuff to perform a if/else is usually more appropriate, and if doing a lot of if/else/elseif checking, a switch/case is probably better.
除此之外，当有很多东西要执行 if/else 通常更合适，如果进行大量 if/else/elseif 检查，switch/case 可能更好。
