Expose --target flag on jsx executable

Valid values are 'es3' and 'es5'.
es3: perform reserved words quoting, don't use defineProperty
es5: default, don't do the above, class methods non-enumerable

bin/jsx

@@ -11,6 +11,13 @@ require('commoner').version(
 }).option(
   '--harmony',
   'Turns on JS transformations such as ES6 Classes etc.'
+).option(
+  '--target [version]',
+  'Specify your target version of ECMAScript. Valid values are "es3" and ' +
+  '"es5". The default is "es5". "es3" will avoid uses of defineProperty and ' +
+  'will quote reserved words. WARNING: "es5" is not properly supported, even ' +
+  'with the use of es5shim, es5sham. If you need to support IE8, use "es3".',
+  'es5'
 ).option(
   '--strip-types',
   'Strips out type annotations.'
@@ -37,7 +44,8 @@ require('commoner').version(
     sourceMap: this.options.sourceMapInline,
     stripTypes: this.options.stripTypes,
     es6module: this.options.es6module,
-    nonStrictEs6Module: this.options.nonStrictEs6Module
+    nonStrictEs6Module: this.options.nonStrictEs6Module,
+    target: this.options.target
   };
   return transform(source, options);
 });

main.js

@@ -64,6 +64,11 @@ function processOptions(opts) {
     options.sourceType = 'nonStrict6Module';
   }
 
+  // Instead of doing any fancy validation, only look for 'es3'. If we have
+  // that, then use it. Otherwise use 'es5'.
+  options.es3 = opts.target === 'es3';
+  options.es5 = !options.es3;
+
   return options;
 }
 
@@ -72,6 +77,11 @@ function innerTransform(input, options) {
   if (options.harmony) {
     visitorSets.push('harmony');
   }
+
+  if (options.es3) {
+    visitorSets.push('es3');
+  }
+
   if (options.stripTypes) {
     // Stripping types needs to happen before the other transforms
     // unfortunately, due to bad interactions. For example,

vendor/fbtransform/visitors.js

@@ -17,6 +17,7 @@ var es7SpreadProperty =
   require('jstransform/visitors/es7-spread-property-visitors');
 var react = require('./transforms/react');
 var reactDisplayName = require('./transforms/reactDisplayName');
+var reservedWords = require('jstransform/visitors/reserved-words-visitors');
 
 /**
  * Map from transformName => orderedListOfVisitors.
@@ -30,7 +31,8 @@ var transformVisitors = {
   'es6-rest-params': es6RestParameters.visitorList,
   'es6-templates': es6Templates.visitorList,
   'es7-spread-property': es7SpreadProperty.visitorList,
-  'react': react.visitorList.concat(reactDisplayName.visitorList)
+  'react': react.visitorList.concat(reactDisplayName.visitorList),
+  'reserved-words': reservedWords.visitorList
 };
 
 var transformSets = {
@@ -44,6 +46,9 @@ var transformSets = {
     'es6-destructuring',
     'es7-spread-property'
   ],
+  'es3': [
+    'reserved-words'
+  ],
   'react': [
     'react'
   ]
@@ -53,6 +58,7 @@ var transformSets = {
  * Specifies the order in which each transform should run.
  */
 var transformRunOrder = [
+  'reserved-words',
   'es6-arrow-functions',
   'es6-object-concise-method',
   'es6-object-short-notation',