JavaScript:当 `condition` 或 `ternary` 语句的 `if` 部分不包括 `===` 或 `>=`

Question

在以下三元 语句的条件 部分，playlist.length 是否等于playlist.length >= 1 ?

var playlist = ["video1", "video2", "video3", "video4", "video5"];

// some code here

alert ((playlist.length) ?
     playlist.length + "video(s) remain in the playlist: " + playlist.join (", ") + "." 
    : "No videos remain in the playlist");

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同样，在下面的代码片段中，! playlist.length 等于 playlist.length === 0 ?

alert ((! playlist.length) ?
     "No videos in the playlist."
    : playlist.length + " video(s) remain in the playlist: " + playlist.join(", ") + ".");

---

This is the first time I've seen an example where the condition portion of a ternary or if statement does not include such a notation as === or >=. So I'm not sure how to interpret this.

Answer 1

0 在 JavaScript 中的 bool 比较中隐式转换为 false。所以当长度为0时，即为假。相反，在 JavaScript 的 bool 比较中，任何其他数字都会隐式转换为 true。因此，当长度不为 0 时为真。

一个简单的测试是使用 !! 来查看“truthy”值

!!1 === true
!!0 === false
!!6 === true