Question

我有以下JSON表示：

var collectionCopy = JSON.parse(JSON.stringify(
 {
   1 : {
        2: "2"
   }  
}
));

为什么我无法使用点表示法访问键“2”（即collectionCopy.1.2）？

Answer 1

您可以使用点表示法仅在语言中的有效标识符上访问对象的属性。

由于数字（或以数字开头的任何数字）不是有效的标识符，因此您只能使用括号表示法来访问它（作为对象的属性）。

Answer 2

这是因为键是字符串而不是实际数字：

访问它使用：

MainActivity

或

AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.validator.ValidatorResources$1) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.digester.ExtendedBaseRules$1) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$5) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$6) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$8) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$9) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$1) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$10) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$11) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$12) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$2) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$3) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$4) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanMap$7) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.BeanUtilsBean$1) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.WrapDynaClass$1) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.WrapDynaClass$2) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}
AGPBI: {"kind":"error","text":"warning: Ignoring InnerClasses attribute for an anonymous inner class","sources":[{}]}
AGPBI: {"kind":"error","text":"(org.apache.commons.beanutils.locale.LocaleBeanUtilsBean$1) that doesn\u0027t come with an","sources":[{}]}
AGPBI: {"kind":"error","text":"associated EnclosingMethod attribute. This class was probably produced by a","sources":[{}]}
AGPBI: {"kind":"error","text":"compiler that did not target the modern .class file format. The recommended","sources":[{}]}
AGPBI: {"kind":"error","text":"solution is to recompile the class from source, using an up-to-date compiler","sources":[{}]}
AGPBI: {"kind":"error","text":"and without specifying any \"-target\" type options. The consequence of ignoring","sources":[{}]}
AGPBI: {"kind":"error","text":"this warning is that reflective operations on this class will incorrectly","sources":[{}]}
AGPBI: {"kind":"error","text":"indicate that it is *not* an inner class.","sources":[{}]}

Relevant docs on accessing properties

为什么我无法使用点表示法访问JSON字典元素？

2 个答案: