Added back jslint prefer-const rule

Issue #132 is fixed in chakracore so adding back the jslint rule of prefer-const.

.eslintrc

@@ -73,7 +73,7 @@ rules:
   # ECMAScript 6
   # list: http://eslint.org/docs/rules/#ecmascript-6
   ## Suggest using 'const' wherever possible
-  prefer-const: 1
+  prefer-const: 2
 
   # Strict Mode
   # list: https://github.com/eslint/eslint/tree/master/docs/rules#strict-mode

lib/repl.js

@@ -87,7 +87,7 @@ class LineParser {
     this.shouldFail = false;
     const wasWithinStrLiteral = this._literal !== null;
 
-    for (let current of line) {
+    for (const current of line) {
       if (previous === '\\') {
         // valid escaping, skip processing. previous doesn't matter anymore
         previous = null;

lib/util.js

@@ -517,7 +517,7 @@ function formatCollectionIterator(ctx, value, recurseTimes, visibleKeys, keys) {
   var nextRecurseTimes = recurseTimes === null ? null : recurseTimes - 1;
   var vals = mirror.preview();
   var output = [];
-  for (let o of vals) {
+  for (const o of vals) {
     output.push(formatValue(ctx, o, nextRecurseTimes));
   }
   return output;

test/parallel/test-http-response-multiheaders.js

@@ -17,13 +17,13 @@ const norepeat = [
 const server = http.createServer(function(req, res) {
   var num = req.headers['x-num'];
   if (num == 1) {
-    for (let name of norepeat) {
+    for (const name of norepeat) {
       res.setHeader(name, ['A', 'B']);
     }
     res.setHeader('X-A', ['A', 'B']);
   } else if (num == 2) {
     const headers = {};
-    for (let name of norepeat) {
+    for (const name of norepeat) {
       headers[name] = ['A', 'B'];
     }
     headers['X-A'] = ['A', 'B'];
@@ -44,7 +44,7 @@ server.listen(common.PORT, common.mustCall(function() {
       {port:common.PORT, headers:{'x-num': n}},
       common.mustCall(function(res) {
         if (n == 2) server.close();
-        for (let name of norepeat) {
+        for (const name of norepeat) {
           assert.equal(res.headers[name], 'A');
         }
         assert.equal(res.headers['x-a'], 'A, B');

test/parallel/test-util-inspect.js

@@ -135,7 +135,7 @@ map.set(1, 2);
 var mirror = Debug.MakeMirror(map.entries(), true);
 var vals = mirror.preview();
 var valsOutput = [];
-for (let o of vals) {
+for (const o of vals) {
   valsOutput.push(o);
 }