Mi JavaScripts.


Declaring variables

For modern JavaScript:

  • let to declare a variable in modern JavaScript (ES6 or later)
  • const for values that must not change, or that you want to throw an error if they are changed.

For JavaScript before ES6:

  • var - to declare a variable in versions of JavaScript before ES6.
    • var variables do not have block scope.
    • They are scoped to the body of the containing function.
    • If var is used outside a function body, it declares a global variable.


Problem Cause Solution
jQuery can’t find plugins: “TypeError: xxxxx is not a function” jQuery is being loaded twice. Remove the second jQuery.