javascript - data?.map这种写法合理吗？炫技？

Question

我见过的一种很奇特的写法，这是炫技吗？

  // 初始化高级筛选选项  const fetchSelectOptions = async () => {    const res = await getMemberSupplierLifecycleStatusList()    if (res.code === 1000) {      const { data } = res      return {        status: data?.map((item) => ({ label: item.message, value: item.code })),      }    }    return {}  }

data?.map这种写法合理吗？

探讨

Answer 1

这是因为不确定接口返回的data一定是个数组结构，万一在没数据时返回了一个null或者undefined，前端就直接报错了。

这是做了下兼容处理。

Answer 2

不算炫技，只是一个帮助简写的语法糖。比如说很久之前我可能会这样写：

data ? data.map(...) : []// or(data && data.length) ? data.map(...) : []

现在的话就只需要 data?.map() 或者 data?.map() || [] 就好了

Answer 3

?. 是个不错的语法糖，你不喜欢不用即可，如果不用，那就

data && data.map(...)// 这种情况如果 data 是 falsy，不会执行 .map

这是正儿八经利用语法取巧的作法，或者

if (data !== undefined && data !== null) {   x = data.map(...)}// 这种情况不适用于表达式，不过可以改成三元运算(data !== undefined && data !== null) ? data.map(...) : undefined

所以单从 ?. 来讨论，很显然，这种写法简单得多。

但是要从逻辑严谨性来说，上面的所有语句都不严谨。至少需要先判断 data 是 Array/ArrayLike 或者 data 有 map 方法。

话说回来，语法糖而已，不喜欢不用即可。

Answer 4

?. 可选链运算符, 与它相似的 含有问号的 ?:, 两个符号相连的 += ==, 甚至三个符号相连的 ===, 它们算炫技的话, 那 ?. 算炫技.

另外 JS 中还有一些比较实用的语法, 比如 ??= 逻辑空赋值, << >> <<= >>= 移位运算, MDN 有总结, 可以系统地了解下: 可选链运算符（?.） - JavaScript | MDN

最后补一下我认为的炫技: let _ = []+[] => _ = '', 花里胡哨无意义的复杂化, 在此基础上纯符号弹框 hello world:

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