when and where i should use const.

when and where i should use const.

hi,

    Q1) i want to use const of javascript and let with jquery 1.9 on my page , can I use it?

    Q2) I have more than one js file on my aspx page, what I have noticed is that in each js file , I have some variables which are declared with var but they are nothing but abbreviation(which are not changed). so can I make them const?