在javascript中，测试属性深深地嵌套在对象图中？ [英] In javascript, test for property deeply nested in object graph?

问题描述

我从CouchDB数据库收集了一些完全不同的复杂JSON对象。每一个都包含很多级别的嵌套属性 - 例如，

  tps_report.personnel_info.productivity.units_sold = 8 
  

我想遍历这些对象并对它们进行操作：例如，

  //写出从每个TPS报告中销售的单位：
 for（i in tpsReports）{
 if（tpsReports [i] .personnel_info.productivity。 units_sold< 10）{
 fireEmployee（）; 
 
 
 
 
 $ b $ p 
 $ b 
问题在于许多TPS报告没有所有这些属性设置。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。 
 
 
 
我看到了两种解决方法，这两种方法对我来说都很难看。
 
 
为嵌套条件单独测试每个属性
 
 
将行包含在try / catch块中以捕获错误并忽略它
 
 
我更喜欢PHP的isset（）函数，不管抛出什么错误你喂它 - 它只是告诉你，你正在寻找的特定变量是否存在。所以，就像 
 
 
  //写下从每个TPS报告中出售的单位：
 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？
解决方案
 
 函数isset（obj，propStr）{
 var parts = propStr.split ）; 
 var cur = obj; 
 for（var i = 0; i< parts.length; i ++）{
 if（！cur [parts [i]]）
 return false; 
 cur = cur [parts [i]]; 
} 
返回true; 
 
 $ / code> 
注意第二个参数是一个字符串，所以异常没有得到在访问不存在的属性上的属性时抛出。
 
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?
解决方案
function isset(obj, propStr) {
    var parts = propStr.split(".");
    var cur = obj;
    for (var i=0; i<parts.length; i++) {
        if (!cur[parts[i]])
            return false;
        cur = cur[parts[i]];
    }
    return true;
}
Note that the second parameter is a string, so the exception doesn't get thrown when accessing a property on a nonexistent property.

                        
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