在javascript中，测试属性是否深深嵌套在对象图中？(In javascript, test for property deeply nested in object graph?)

 我从CouchDB数据库中获得了一组完全不同的复杂JSON对象。 每个包含很多级别的嵌套属性 - 例如， 
 
tps_report.personnel_info.productivity.units_sold = 8  
 
 我想通过这些对象进行迭代并对它们进行处理：例如， 
 
// writes units sold from each TPS report:
for (i in tpsReports) {
  if (tpsReports[i].personnel_info.productivity.units_sold < 10) {
    fireEmployee();
  }
}
 
 问题是许多TPS报告没有设置所有这些属性。 因此，如果我尝试这样做，那么在第一次循环获取到没有“personnel_info”属性的报告时，会出现错误，从而尝试查找“undefined”的“productivity”属性。 我宁愿发生的是条件只是跳过它并继续。 
 
 我看到了两种方式，这两种方式对我来说都显得很丑陋 
 
 
 
 分别使用嵌套条件测试每个属性 
 
 
 将行放在try / catch块中以捕获错误并忽略它 
 
 
 我更喜欢的是PHP的isset（）函数，它不会抛出错误，无论提供什么内容 - 它只会告诉你你正在寻找的特定变量是否存在。 所以，就像 
 
// writes units sold from each TPS report:
for (i in tpsReports) {
  if (isset(tpsReports[i].personnel_info.productivity.units_sold)){
    if (tpsReports[i].personnel_info.productivity.units_sold < 10) {
      fireEmployee();
    }
  }
}
 
 有什么想法吗？ 

I've got a collection of disparate, complex JSON objects from a CouchDB database. Each contains many levels of nested properties--for example, 
 
tps_report.personnel_info.productivity.units_sold = 8  
 
I want to iterate through these objects and do stuff with them: for instance, 
 
// writes units sold from each TPS report:
for (i in tpsReports) {
  if (tpsReports[i].personnel_info.productivity.units_sold < 10) {
    fireEmployee();
  }
}
 
The problem is that many TPS reports don't have all these properties set. So if I try this, I'll get an error the first time the loop gets to a report without the "personnel_info" property and thus tries to find the "productivity" property of "undefined." What I'd rather happen is that the conditional just skips it and continues.
 
I see two ways around this, both of which seem ugly to me
 
 
 
test for each property separately with nested conditionals
 
 
enclose the line in a try/catch block to catch the error and ignore it
 
 
What I'd prefer would be something like PHP's isset() function, which won't throw an error regardless of what you feed it--it'll just tell you whether the particular variable you're looking for exists or not. So, like
 
// writes units sold from each TPS report:
for (i in tpsReports) {
  if (isset(tpsReports[i].personnel_info.productivity.units_sold)){
    if (tpsReports[i].personnel_info.productivity.units_sold < 10) {
      fireEmployee();
    }
  }
}
 
Any thoughts?

原文：https://stackoverflow.com/questions/4343028