Why use the `var` keyword in Vue.js?
Why do the docs use var and avoid ES6 features? I'd say to support lowest common denominator, ie, worst browser.
Since Vue can be included as a plain old <script> tag (UMD / global, no build system) and supports all ES5-compliant browsers (IE9+), they keep the documentation consistent.
Use whatever you...
- Feel comfortable using, and
- Is supported by the target production environment
- your build system (if you're using one) can help transpile ES6 code to a lower language level
Besides the lowest common denominator arguments I would like to point that var and let have different semantics.
When using var variables are function scoped and they get hoisted. When using let they are blocked scoped and they don't get hoisted.
So even if let and const are standard they (probably) won't replace var any time soon.