chore: update eslint rules to disallow var usage

Enforce the use of `let` and `const` by using elsint rules.
When creating the eslint configuration, I had assumed that
`extends: eslint:recommended` would have covered this, but
apparently not!

Existing usage of `var` fixed with `npm run lint -- --fix`.

Fixes: cloudevents#97

Signed-off-by: Lance Ball <[email protected]>

Author: lance

.eslintrc

@@ -6,6 +6,7 @@
     "mocha": true
   },
   "rules": {
+    "no-var": "error",
     "space-before-function-paren": ["error", "never"],
     "standard/no-callback-literal": "off",
     "arrow-spacing": "error",

index.js

@@ -1,3 +1,3 @@
-var Cloudevent = require("./lib/cloudevent.js");
+const Cloudevent = require("./lib/cloudevent.js");
 
 module.exports = Cloudevent;

lib/formats/json/parser.js

@@ -19,7 +19,7 @@ const asJSON = (v) => (isString(v) ? JSON.parse(v) : v);
 
 // Level 0 of validation: is that string? is that JSON?
 function validateAndParse(payload) {
-  var json =
+  const json =
     Array.of(payload)
       .filter((p) => isDefinedOrThrow(p, nullOrIndefinedPayload))
       .filter((p) => isStringOrObjectOrThrow(p, invalidPayloadTypeError))

lib/specs/spec_1.js

@@ -109,7 +109,7 @@ function Spec1(_caller) {
  * Check the spec constraints
  */
 Spec1.prototype.check = function(ce) {
-  var toCheck = (!ce ? this.payload : ce);
+  const toCheck = (!ce ? this.payload : ce);
 
   if (!isValidAgainstSchema(toCheck)) {
     const err = new TypeError("invalid payload");