What are the differences between Python Dictionaries vs Javascript Objects?

From :

In Python, dictionaries are a form of mapping type. They can be
initialized using a sequence of comma-separated name: value pairs,
enclosed in curly braces. They are accessed using array notation
involving square braces. The key can be any hashable, including
numbers and strings.

In Javascript, a dictionary is the same as an object. It can be
initialized using the same syntax as Python. The key can be a number,
a string, or an identifier. Because the dictionary is also an object,
the elements can be accessed either using array notation, e.g. b[i],
or using property notation, e.g. b.i.

Consider an identifier used in an initializer, such as

 b = {i:j} 

In Python both i and j are evaluated, but in Javascript, only j is evaluated. In Javascript you also have the
privilege of writing in the dot notation, using the identifier i.
Hence in Python,

 i='k'
 j=1
 b = {i:j}
 b['k'] # -> 1 

In Javascript,

 i='k'
 j=1
 b = {i:j}
 b['i'] // -> 1
 b.i // -> 1
 // b[i], b['k'] and b.k are not defined 

In Javascript, using the identifier in dot notation is completely identical in all cases to
using a string that “looks like” the identifier in array notation.
Hence,
b = { ‘i’:1 } ;
b[‘i’] // -> 1
b.i // -> 1 When a number or boolean is used in a dictionary, Javascript will access the element using a string representation of
the number or boolean. Not so in Python — a string and a number (or
boolean) are different hashables.

If you are interested in differences between both languages, then look at ans