javascript - 如何将链式属性从字符串转换为 javascript 中的变量

Question

我有这个存储在字符串中的变量

  var employee  = {
        name: 'person',
        job: {
           post: 'developer',
           since: 2010,
           desk: {
              number: '1',
        }
    }
  };

如何从字符串中获取钥匙串(keychain)值，例如

  var variable = "job.desk.number";
  console.log(variable);
  //this should return 1

更新 3!

@T.J.克劳德的答案其实是最好的答案。

他的功能快速而整洁。 :) 快乐!

Answer 1

拆分字符串，这样你就有了一个键数组，然后循环遍历它们，依次从对象中获取每个键，记住你从对象中得到的最后一个东西:

var value = variable.split('.').reduce(function(prev, key) {
  return prev[key];
}, employee);
snippet.log(value);

例子:

var employee  = {
  name: 'person',
  job: {
    post: 'developer',
    since: 2010,
    desk: {
      number: '1',
    }
  }
};

var variable = "job.desk.number";
var value = variable.split('.').reduce(function(prev, key) {
  return prev[key];
}, employee);
snippet.log(value);

<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

请注意，Array#reduce 是 ES5 的东西，所以它存在于所有现代浏览器中，但不是一些较旧的浏览器。不过，它可以填充/填充。或者，如果您只是喜欢使用 for 循环:

var keys = variable.split('.');
var value = employee;
var index;
for (index = 0; index < keys.length; ++index) {
    value = value[keys[index]];
}
snippet.log(value);

例子:

var employee  = {
  name: 'person',
  job: {
    post: 'developer',
    since: 2010,
    desk: {
      number: '1',
    }
  }
};

var variable = "job.desk.number";
var keys = variable.split('.');
var value = employee;
var index;
for (index = 0; index < keys.length; ++index) {
    value = value[keys[index]];
}
snippet.log(value);

<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>