安全地访问Javascript嵌套对象 [英] Access Javascript nested objects safely

问题描述

我有基于json的数据结构，对象包含嵌套对象。为了访问特定的数据元素，我一直在链接对象属性的引用。例如：

I have json based data structure with objects containing nested objects. In order to access a particular data element I have been chaining references to object properties together. For example:

var a = b.c.d;

如果未定义b或b.c，则会失败并显示错误。但是，我希望得到一个值，如果它存在，否则只是未定义。在不检查链中的每个值是否存在的情况下，最好的方法是什么？

If b or b.c is undefined, this will fail with an error. However, I want to get a value if it exists otherwise just undefined. What is the best way to do this without having to check that every value in the chain exists?

我想尽可能保持这种方法的一般性，所以我不喜欢必须添加大量辅助方法，如：

I would like to keep this method as general as possible so I don't have to add huge numbers of helper methods like:

var a = b.getD();

或

var a = helpers.getDFromB(b);

我也想尽量避免使用try / catch构造，因为这不是错误所以使用try / catch似乎错位了。这是合理的吗？

I also want to try to avoid try/catch constructs as this isn't an error so using try/catch seems misplaced. Is that reasonable?

任何想法？

推荐答案

你可以创建一种基于属性名称数组访问元素的通用方法，该属性名称数组被解释为通过属性的路径：

You can create a general method that access an element based on an array of property names that is interpreted as a path through the properties:

function getValue(data, path) {
    var i, len = path.length;
    for (i = 0; typeof data === 'object' && i < len; ++i) {
        data = data[path[i]];
    }
    return data;
}

然后你可以用以下方式调用它：

Then you could call it with:

var a = getValue(b, ["c", "d"]);

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