Javascript 对象属性 - 如果不存在则创建属性

Question

我正在尝试以最优雅的方式执行这段代码:

if (internalTableName in self.columnMap &&
    internalColumnName in self.columnMap[internalTableName]) {
    console.error('dupelicates');
}
else {
    try {
        self.columnMap[internalTableName][internalColumnName] = logicalColumnName;
    } catch (err) {
        self.columnMap[internalTableName] = {};
        self.columnMap[internalTableName][internalColumnName] = logicalColumnName;
    }
}

我可以将 try/catch block 变成:

if (internalTableName in self.columnMap &&
    internalColumnName in self.columnMap[internalTableName]) {
    console.error('dupelicates');
}
else {
    if (internalTableName in self.columnMap) {
        self.columnMap[internalTableName][internalColumnName] = logicalColumnName;
    }
    else {
        self.columnMap[internalTableName] = {};
        self.columnMap[internalTableName][internalColumnName] = logicalColumnName;

    }
}

我想知道 Javascript 是否提供了一些运算符来检查无效性，从而使该逻辑以更优雅的方式编写并减少 IF 子句。

谢谢

Answer 1

常见的模式是使用 || operator :

self.columnMap[internalTableName] = self.columnMap[internalTableName] || {};
self.columnMap[internalTableName][internalColumnName] = logicalColumnName;