javascript if-else 语句的简写
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Shorthand for if-else statement
提问by Meek
I have some code with a lot of if/else statements similar to this:
我有一些代码，其中包含很多与此类似的 if/else 语句：
var name = "true";
if (name == "true") {
var hasName = 'Y';
} else if (name == "false") {
var hasName = 'N';
};
But is there a way to make these statements shorter? Something like ? "true" : "false"...
但是有没有办法让这些陈述更短？像? "true" : "false"...
回答by Tushar Gupta - curioustushar
Using the ternary :?operator[spec].
var hasName = (name === 'true') ? 'Y' :'N';
The ternary operator lets us write shorthand if..elsestatements exactly like you want.
三元运算符让我们可以if..else完全按照您的意愿编写速记语句。
It looks like:
看起来像：
(name === 'true')- our condition
(name === 'true')- 我们的条件
?- the ternary operator itself
?- 三元运算符本身
'Y'- the result if the condition evaluates to true
'Y'- 条件评估为真时的结果
'N'- the result if the condition evaluates to false
'N'- 如果条件评估为假的结果
So in short (question)?(result if true):(result is false), as you can see - it returns the value of the expression so we can simply assign it to a variable just like in the example above.
简而言之(question)?(result if true):(result is false)，正如您所看到的 - 它返回表达式的值，因此我们可以像上面的示例一样简单地将其分配给一个变量。
回答by Benjamin Gruenbaum
You can use an object as a map:
您可以将对象用作地图：
var hasName = ({
"true" : "Y",
"false" : "N"
})[name];
This also scales nicely for many options
这也适用于许多选项
var hasName = ({
"true" : "Y",
"false" : "N",
"fileNotFound" : "O"
})[name];
(Bonus point for people getting the reference)
（获得参考的人的奖励积分）
Note: you should use actual booleans instead of the string value "true" for your variables indicating truth values.
注意：对于表示真值的变量，您应该使用实际的布尔值而不是字符串值“true”。
回答by Eswara Reddy
Try this
试试这个
hasName = name ? 'Y' : 'N';
回答by Gautam3164
Try like
试试像
var hasName = 'N';
if (name == "true") {
hasName = 'Y';
}
Or even try with ternary operatorlike
或者甚至尝试ternary operator像
var hasName = (name == "true") ? "Y" : "N" ;
Even simply you can try like
即使只是你可以尝试像
var hasName = (name) ? "Y" : "N" ;
Since name has either Yesor Nobut iam not sure with it.
由于名称具有Yes或No但我不确定它。
回答by Abijeet Patro
Most answers here will work fine if you have just twoconditions in your if-else. For more which is I guess what you want, you'll be using arrays.
Every names corresponding element in namesarray you'll have an element in the hasNamesarray with the exact same index. Then it's a matter of these four lines.
如果您two的 if-else 中只有条件，这里的大多数答案都可以正常工作。对于更多我猜你想要什么，你将使用数组。names数组中的每个名称对应的元素您将在数组中拥有一个hasNames具有完全相同索引的元素。那么就是这四行的问题了。
names = "true";
var names = ["true","false","1","2"];
var hasNames = ["Y","N","true","false"];
var intIndex = names.indexOf(name);
hasName = hasNames[intIndex ];
This method could also be implemented using Objects and properties as illustrated by Benjamin.
此方法也可以使用对象和属性来实现，如Benjamin 所示。
