尝试访问sqlite serialize（node.js）中的常规对象属性时出错

Question

当使用 sqlite3 模块中的db.serialize()（sqlite3 on npm）时，访问对象属性会出错，这不是＆＃39; db之外的问题。 serialize（）`call。

有问题的代码：

var files = [];
var fragments = {};

// [...]

function massInsertIntoDB() {
    // This works fine...
    console.log('Files length: ', files.length);
    console.log('Fragments length: ', Object.keys(fragments).length);

    db.serialize(() => {
        // Still works fine
        console.log('Files length: ', files.length);

        // -----------------
        // ERROR
        // -----------------
        console.log('Fragments length: ', Object.keys(fragments).length);
        // [...]
    });
}

控制台输出：

Files length:  292582
Fragments length:  20242
Files length:  292582

/Users/Jonas/dev/electron-projects/tag-file-search/file-search/sqlite-insert-and-search.js:78
    console.log('Fragments length: ', Object.keys(fragments).length);
                                         ^

TypeError: Cannot convert undefined or null to object
    at Function.keys (native)
    at Database.<anonymous> (/Users/Jonas/dev/electron-projects/tag-file-search/file-search/sqlite-insert-and-search.js:78:46)
    at massInsertIntoDB (/Users/Jonas/dev/electron-projects/tag-file-search/file-search/sqlite-insert-and-search.js:75:6)
    at Interface.<anonymous> (/Users/Jonas/dev/electron-projects/tag-file-search/file-search/sqlite-insert-and-search.js:195:3)
    at emitNone (events.js:72:20)
    at Interface.emit (events.js:166:7)
    at Interface.close (readline.js:285:8)
    at ReadStream.onend (readline.js:94:10)
    at emitNone (events.js:72:20)
    at ReadStream.emit (events.js:166:7)

我不知道为什么这不起作用，我们将非常感谢任何帮助！