var : var is a global variable that can be define and re-assign from anywhere and anytime.
let : let is a block and global variable. which can be re-assigned but cannot be defined with the same name and keyword. and cannot be accessed from outside if used inside a specific function or loop function.
const : const is a block and global variable. which can not be re-assigned and cannot be defined with the same name and keyword. and cannot be accessed from outside if used inside a specific function or loop function.
arrow function : arrow function is a advance label function. This functions have to be written like variables and coding with it makes the codes look nicer and easier to code in comparison.
Regular function : Regular function is a basic label function. This function is relatively more writeable than the arrow function
Template String : I can easily write the codes and create a dynamic website using the template String.