Snippet: https://gist.github.com/smks/d41c2d6778a3a23965eaea726af2bd01 The let statement declares a block scope local variable, optionally initializing it to a value. Constants are block-scoped, much like variables defined using the let statement. The value of a constant cannot change through re-assignment, and it can't be redeclared. http://www.opencanvas.co.uk/ References: http://es6-features.org/#Constants https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Grammar_and_types#Constants