Add tool to transpile JavaScript sources using Babel (#3009)

JerryScript-DCO-1.0-Signed-off-by: Daniella Barsony bella@inf.u-szeged.hu

tools/babel/.babelrc

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+{
+  "plugins": [
+    "@babel/plugin-transform-function-name",
+    "@babel/plugin-proposal-object-rest-spread",
+    "@babel/plugin-transform-block-scoping",
+    "@babel/plugin-transform-destructuring",
+    "@babel/plugin-transform-block-scoped-functions",
+    "@babel/plugin-transform-unicode-regex",
+    "@babel/plugin-transform-sticky-regex",
+    "@babel/plugin-transform-spread",
+    "@babel/plugin-transform-parameters",
+    "@babel/plugin-transform-object-super",
+    "@babel/plugin-transform-new-target",
+    "@babel/plugin-transform-literals",
+    "@babel/plugin-transform-instanceof"
+  ]
+}

tools/babel/README.md

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+# Converting incompatible features with Babel
+To run ES6 sources with JerryScript that use unsupported language features, you can use Babel to transpile your code, which will output a semantically equivalent source file, where the unsupported features are replaced with ES5.1 code.
+Babel is a JavaScript compiler that is used to convert ES2015+ code into a backward-compatible version. You can find more information [here](https://babeljs.io/).
+
+## Example
+
+```javascript
+//Before
+const fn = () => 1;
+
+//After conversion
+
+var fn = function fn() {
+  return 1;
+};
+```
+## Table of Contents
+* **[Getting ready](#getting-ready)**
+  * Installing node.js and npm
+* **[Using babel](#using-babel)**
+* **[Missing features/Polyfill](#missing-features)**
+
+## Getting ready [](#getting-ready)
+
+### 1. **Node.js and npm**
+
+Start by updating the packages with
+
+`$ sudo apt update`
+
+Install `nodejs` using the apt package manager
+
+`$ sudo apt install nodejs`
+
+Check the version of **node.js** to verify that it installed
+
+```bash
+$ nodejs --version
+Output: v8.10.0
+```
+
+Next up is installing **npm** with the following command
+
+`$ sudo apt install npm`
+
+Verify installation by typing:
+
+```bash
+$ npm --version
+Output: 6.10.2
+```
+
+### 2. Using babel [](#using-babel)
+
+Assuming you're in the tools/babel folder,
+
+`$ sudo npm install`
+
+After installing the dependencies it is ready to use.
+
+Place the files/directories you want transpiled to the babel folder and run
+
+`$ npm run transpile [name of input file/directory] [(OPTIONAL)name of output file/directory]`
+
+If you want to use the same name, then only give the name once.
+
+#### Missing features/Polyfill [](#missing-features)
+Some features aren't implemented yet and found no babel plug-in for them.
+
+* [Array.from](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from)
+* [Array.prototype.fill](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/fill)
+* [String.prototype.codePointAt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/codePointAt)
+
+In the case you encounter those, use the polyfill found on the linked sites. Also, **be aware** there could be more.

tools/babel/package.json

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+{
+  "name": "jerryscript",
+  "description": "Ultra-lightweight JavaScript engine for the Internet of Things.",
+  "scripts": {
+    "transpile": "scripty"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/jerryscript-project/jerryscript.git"
+  },
+  "license": "Apache-2.0",
+  "devDependencies": {
+    "@babel/cli": "^7.4.4",
+    "@babel/core": "^7.4.5",
+    "@babel/plugin-proposal-object-rest-spread": "^7.5.5",
+    "@babel/plugin-transform-block-scoped-functions": "^7.2.0",
+    "@babel/plugin-transform-block-scoping": "^7.4.4",
+    "@babel/plugin-transform-destructuring": "^7.4.4",
+    "@babel/plugin-transform-function-name": "^7.4.4",
+    "@babel/plugin-transform-instanceof": "^7.2.0",
+    "@babel/plugin-transform-literals": "^7.2.0",
+    "@babel/plugin-transform-new-target": "^7.4.4",
+    "@babel/plugin-transform-object-super": "^7.2.0",
+    "@babel/plugin-transform-parameters": "^7.4.4",
+    "@babel/plugin-transform-spread": "^7.2.2",
+    "@babel/plugin-transform-sticky-regex": "^7.2.0",
+    "@babel/plugin-transform-unicode-regex": "^7.4.4",
+    "scripty": "^1.9.1"
+  }
+}

tools/babel/scripts/transpile.sh

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+#!/usr/bin/env bash
+
+# Copyright JS Foundation and other contributors, http://js.foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+if [[ "$#" -gt 2 || "$#" -lt 1 ]]; then
+  echo "Usage: $0 input [output]"
+  echo "* input: name of input directory/file"
+  echo "* output: name of output directory/file (same as input if not given)"
+  exit 1
+fi
+
+if [[ ! -d $1 && ! -f $1 ]]; then
+  echo "Error: $1 is not a file or directory"
+  exit 1
+fi
+
+FLAG='--out-file'
+if [[ -d $1 ]]; then
+  FLAG='--out-dir'
+fi
+
+if [[ "$#" -eq 1 ]]; then
+  ./node_modules/.bin/babel $1 $FLAG $1 --verbose
+else
+  ./node_modules/.bin/babel $1 $FLAG $2 --verbose
+fi