在学习 JavaScript 的解构赋值语法时，遇到了一个想不明白的语法

代码如下

var metadata = {
    title: "Scratchpad",
    translations: [
       {
        locale: "de",
        localization_tags: [ ],
        last_edit: "2014-04-14T08:43:37",
        url: "/de/docs/Tools/Scratchpad",
        title: "JavaScript-Umgebung"
       },
       {
        locale: "fg",
        localization_tags: [ ],
        last_edit: "2015-04-14T08:43:37",
        url: "/de/docs/Tools/Scratch",
        title: "JavaScript"
       }
    ],
    url: "/en-US/docs/Tools/Scratchpad"
};

var {title: englishTitle, translations: [{title: localeTitle}]} = metadata;
console.log(englishTitle); // "Scratchpad"
console.log(localeTitle); // "JavaScript-Umgebung"

title: englishTitle 取 metadata 对象中的 title 的值并赋值给变量 englishTitle 这个能看懂

translations: [{title: localeTitle}] 这里 title: localeTitle 这个能理解 translations: [{}] 这个语法想不通是啥意思了