Dot Notation vs Bracket Notation

const newObject = {};

newObject.0 = "value 1" 
Result: Error as you cannot have number

newObject.key1 = "value 1" 
// newObject = {key1: "value 1"}

newObject["key1"] = "value 1" 
// newObject = {key1: "value 1"}

newObject["key2"] = "value 2"
// newObject = {key1: "value 1", key2: "value 2"}

newObject[0] = "value 0" 
//newObject = {0: "value 0", key1: "value 1", key2: "value 2"}

newObject["0"] = "value 00" 
//newObject = {0: "value 00", key1: "value 1", key2: "value 2"}

newObject["1"] = "value 01" 
//newObject = {0: "value 00", 1: "value 01", key1: "value 1", key2: "value 2"}

Dot notation:

• Property identifies can only be alphanumeric (and _ and $)

• Property identifiers cannot start with a number.

• Property identifiers cannot contain variables.

• OK — obj.prop_1, obj.prop$

• Not OK — obj.1prop, obj.prop name

Bracket notation:

• Property identifiers have to be a String or a variable that references a String.

• It is okay to use variables, spaces, and Strings that start with numbers

• OK — obj["1prop"], obj["prop name"]