Javascript in several forms in brackets

There are several forms

There arr = [];
There are b = [1,1,1 ];
There c = b [0 ];
There obj = { 'name': 'tom', 'age': 23 };
There are d = obj [ 'name'];

and b represents an array arr defined

c indicating a target value of the array

d representation of an object in a property
description link: https: //blog.csdn.net/weixin_43649130/article/details/91948161