Javascript 速记三元运算符
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Javascript shorthand ternary operator
提问by Web_Designer
I know that in php 5.3 instead of using this redundant ternary operator syntax:
我知道在 php 5.3 中而不是使用这种冗余的三元运算符语法：
startingNum = startingNum ? startingNum : 1
...we can use a shorthand syntax for our ternary operators where applicable:
...我们可以在适用的情况下为我们的三元运算符使用速记语法：
startingNum = startingNum ?: 1
And I know about the ternary operator in javascript:
我知道 javascript 中的三元运算符：
startingNum = startingNum ? startingNum : 1
...but is there a shorthand?
...但是有速记吗？
回答by Brad Christie
var startingNumber = startingNumber || 1;
Something like that what you're looking for, where it defaults if undefined?
像你正在寻找的东西，如果未定义它默认在哪里？
var foo = bar || 1; // 1
var bar = 2;
foo = bar || 1; // 2
By the way, this works for a lot of scenarios, including objects:
顺便说一下，这适用于很多场景，包括对象：
var foo = bar || {}; // secure an object is assigned when bar is absent
回答by Adam Rackis
||will return the first truthy value it encounters, and can therefore be used as a coalescing operator, similar to C#'s ??
||将返回它遇到的第一个真值，因此可以用作合并运算符，类似于 C# ??
startingNum = startingNum || 1;
回答by Tadeck
Yes, there is:
就在这里：
var startingNum = startingNum || 1;
In general, expr1 || expr2works in the following way (as mentioned by the documentation):
通常，expr1 || expr2按以下方式工作（如文档所述）：
Returns
expr1if it can be converted totrue; otherwise, returnsexpr2.Thus, when used withBooleanvalues,||returnstrueif either operand istrue; if both arefalse, returnsfalse.
expr1如果可以转换为true，则返回；否则，返回expr2。因此，当与Boolean值一起使用时，如果任一操作数是，则||返回；如果两者都是，则返回。truetruefalsefalse
回答by Daniel
var startingNum = startingNum || 1;
In this case, you can use the OR operator.
在这种情况下，您可以使用 OR 运算符。
回答by John Pace
The above answers are correct. In JavaScript, the following statement:
以上答案都是正确的。在 JavaScript 中，以下语句：
startingNum = startingNum ? otherNum : 1
can be expressed as
可以表示为
startingNum = otherNum || 1
Another scenario not covered here is if you want the value to return false when not matched. The JavaScript shorthand for this is:
此处未涵盖的另一种情况是，如果您希望该值在不匹配时返回 false。对此的 JavaScript 简写是：
startingNum = startingNum ? otherNum : 0
But it can be expressed as
但可以表示为
startingNum = startingNum && otherNum
Just wanted to cover another scenario in case others were looking for a more generalized answer.
只是想涵盖另一种情况，以防其他人正在寻找更普遍的答案。
回答by a2441918
startingNum = startingNum || 1
If you have a condition with null, like
如果您的条件为 null，例如
startingNum = startingNum ? startingNum : null
you can use '&&'
您可以使用 '＆＆'
startingNum = startingNum && startingNum
回答by xxjjnn
To make a ternary like:
制作一个三元像：
boolean_condition ? true_result : false_result
in javascript, you can do:
在 javascript 中，您可以执行以下操作：
(boolean_condition && true_result ) || false_result;
Example:
例子：
(true && 'green') || 'red';
=> "green"
(false && 'green') || 'red';
=> "red"
