JavaScript替代方案 [英] JavaScript if alternative
问题描述
这段代码代表什么？我知道它是某种如果替代语法......
What does this bit of code represent? I know it's some kind of if alternative syntax...
pattern.Gotoccurance.score != null ? pattern.Gotoccurance.score : '0'
更新：
这种编码有什么需要？这是效率更高还是效率相同的缩短版本？
What's the need for this sort of coding? Is this more efficient or just a shortened version with the same efficiency?
推荐答案
这是条件运算符，它相当于这样：
It is the conditional operator, it is equivalent to something like this:
if (pattern.Gotoccurance.score != null) {
pattern.Gotoccurance.score;
} else {
'0';
}
但我认为你发布的代码中缺少一个赋值语句，比如这个：
But I think that an assignment statement is missing in the code you posted, like this:
var score = pattern.Gotoccurance.score !=null ? pattern.Gotoccurance.score : '0';
如果<分配得分变量code> pattern.Gotoccurance.score 不为空：
The score variable will be assigned if pattern.Gotoccurance.score is not null:
var score;
if (pattern.Gotoccurance.score != null) {
score = pattern.Gotoccurance.score;
} else {
score = '0';
}
在JavaScript中执行此类默认值分配的常见模式是使用逻辑OR运算符（ || ）：
A common pattern to do this kind of 'default value' assignments in JavaScript is to use the logical OR operator (||) :
var score = pattern.Gotoccurance.score || '0';
pattern.Gotoccurance.score 的值仅当该值不是 falsy 时才会被分配到得分变量（假值为 false ， null ， undefined ， 0 ，零 - 长度字符串或 NaN ）。
The value of pattern.Gotoccurance.score will be assigned to the score variable only if that value is not falsy (falsy values are false, null, undefined, 0, zero-length string or NaN).
否则，如果它是假的'0'将被分配。
Otherwise, if it's falsy '0' will be assigned.
更新：性能相当，你应该专注于可读性，我尝试使用表达式上的三元运算符非常简单，你也可以改进格式，将它分成两行以使其更具可读性：
Update: The performance will be equivalent, you should focus on readability, I try to use the ternary operator on expressions that are very simple, and you can also improve the formatting, splitting it up in two lines to make it more readable:
var status = (age >= 18) ? "adult"
: "minor";
相关问题：
- To Ternary or Not To Ternary?
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