Include babelify step in browserify calls

This allows using ES6 syntax in our code, while maintaining backwards
compatibility for the generated file.

.babelrc

@@ -0,0 +1,6 @@
+{
+    "presets": ["es2015"],
+    "plugins": [
+        "transform-runtime"
+    ]
+}

.eslintrc

@@ -76,7 +76,7 @@
         "templateStrings": true
     },
     "env": {
-        // "es6": true,
+        "es6": true,
         "node": true,
         "browser": true
     },

Makefile

@@ -13,6 +13,12 @@ dist: build
 
 endif
 
+NODE := node # pass NODE=nodejs on Debian without package nodejs-legacy
+NODECHK := $(shell $(NODE) ./check-node-version.js)
+ifneq ($(NODECHK),OK)
+$(error "Node not found or wrong version")
+endif
+
 # Export these variables for use in contrib Makefiles
 export BUILDDIR = $(realpath build)
 export BROWSERIFY = $(realpath ./node_modules/.bin/browserify)
@@ -33,7 +39,7 @@ lint: $(NIS) katex.js server.js cli.js $(wildcard src/*.js) $(wildcard test/*.js
 	./node_modules/.bin/eslint $(filter-out %.stamp,$^)
 
 build/katex.js: katex.js $(wildcard src/*.js) $(NIS)
-	$(BROWSERIFY) $< --standalone katex > $@
+	$(BROWSERIFY) -t [ babelify ] $< --standalone katex > $@
 
 build/katex.min.js: build/katex.js
 	$(UGLIFYJS) < $< > $@
@@ -92,7 +98,7 @@ compress: build/katex.min.js build/katex.min.css
 	@printf "Total:                 %6d\n" "${TOTAL}"
 
 serve: $(NIS)
-	node server.js
+	$(NODE) server.js
 
 test: $(NIS)
 	JASMINE_CONFIG_PATH=test/jasmine.json node_modules/.bin/jasmine

check-node-version.js

@@ -0,0 +1,16 @@
+"use strict";
+
+var v = process.version;
+v = v.replace(/^v/,"");
+v = v.split(".");
+v = v.map(function(s){
+    return parseInt(s);
+});
+var a = v[0], b = v[1], c = v[2];
+if (a < 6 || (a == 6 && b < 5)) {
+    console.error("Node 6.5 or later required for development. " +
+                  "Version " + process.version + " found");
+    process.exit(1);
+} else {
+    console.log("OK");
+}

contrib/auto-render/Makefile

@@ -6,4 +6,4 @@ $(BUILDDIR)/contrib/auto-render.min.js: $(BUILDDIR)/auto-render.js
 	$(UGLIFYJS) < $< > $@
 
 $(BUILDDIR)/auto-render.js: auto-render.js
-	$(BROWSERIFY) $< --standalone renderMathInElement > $@
+	$(BROWSERIFY) -t [ babelify ] $< --standalone renderMathInElement > $@

package.json

@@ -15,6 +15,9 @@
   ],
   "license": "MIT",
   "devDependencies": {
+    "babel-plugin-transform-runtime": "^6.15.0",
+    "babel-preset-es2015": "^6.18.0",
+    "babelify": "^7.3.0",
     "browserify": "^13.3.0",
     "clean-css": "^3.4.23",
     "eslint": "^3.13.0",

server.js

@@ -2,6 +2,7 @@
 var fs = require("fs");
 var path = require("path");
 
+var babelify = require("babelify");
 var browserify = require("browserify");
 var express = require("express");
 var glob = require("glob");
@@ -25,7 +26,9 @@ var serveBrowserified = function(file, standaloneName) {
             files = [path.join(__dirname, file)];
         }
 
-        var options = {};
+        var options = {
+            transform: [babelify]
+        };
         if (standaloneName) {
             options.standalone = standaloneName;
         }