在 N 级 javascript 中调用对象属性 [英] calling object properties in N levels javascript

问题描述

我正在使用 mongodb 和 ajax 调用来检索数据.当谈到 javascript 对象时，我用来生成 html 的属性有时不存在.看看这个电话:

I'm using mongodb and ajax calls to retrieve data. When it turns to javascript object, the properties that I use to generate html sometimes don't exist. Look at this call:

$.ajax({
        url: 'api/v1/mention/'+id,
        type: "GET",
        dataType: "json",
        data : {login : "demo"},
        success: function(mention) {
            display_mention_text(mention.texto);
        }
    });

在这种情况下，我调用的是mention.texto，但可以是mention.picture 或任何属性.有时它是未定义的并使应用程序崩溃.

In this case i'm calling mention.texto, but could be mention.picture or any properties. Sometimes it is undefined and crashes the app.

这个方法从一个对象调用一个属性，如果它是 undefined ，则返回一个空字符串.调用此方法的一些示例(第一个是对象，另一个是属性):

This method calls a property from a object and if its undefined , return an empty string. Some examples for calling this method(the first one is an object, the other are properties):

get_property(mention,"text")
get_property(mention,"user","name")
get_property(mention,"picture")

方法定义如下:

function get_property(obj){
    var args = Array.prototype.slice.call(arguments),
     obj = args.shift();
    if (checkNested(obj,args)) {
       //what should I do here?
    } else{
                   //the property is undefined and returns ""
        "";
    };
}


    //check if a object has N levels of propertys
function checkNested(obj /*, level1, level2, ... levelN*/) {
  var args = Array.prototype.slice.call(arguments),
      obj = args.shift();

  for (var i = 0; i < args.length; i++) {
    if (!obj.hasOwnProperty(args[i])) {
      return false;
    }
    obj = obj[args[i]];
  }
  return true;
}

在第一个方法 get_property 中，如果该属性确实存在，我该如何调用它??我会将对象和他的属性作为一个数组，如:对象

In the first method get_property, if the property do exist, how do I call that?? I would have the object and his propertys as an array like: object

params = ["user","name"]

但我不能像下面这样调用:

but I can't call like following:

object.["user","name"]

推荐答案

用 for 循环替换 get_property 函数中的 if 语句来自 checkNested 函数.然后返回找到的值或 ""，而不是返回 true 或 false.

Replace the if statement in the get_property function with the for loop from the checkNested function. Then instead of returning true or false, return the value found or "".

function get_property(obj){
    var args = Array.prototype.slice.call(arguments),
        obj = args.shift();

     // Here's your 'for' loop. The 'if' statement is gone.
    for (var i = 0; i < args.length; i++) {
        if (!obj.hasOwnProperty(args[i])) {
          return "";   // I changed the value of this 'return' statement
        }
        obj = obj[args[i]];
    }
    return obj;  // I change the value of this 'return' statement
}

同样，我所做的只是将您自己的代码从一个函数复制粘贴到另一个函数，然后更改 return 语句的值.

Again, all I did was copy paste your own code from one function to the other, and change the values of the return statements.

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