SyntaxError: Unexpected token function - Async Await Nodejs
Javascriptnode.jsExpressAsynchronousAsync AwaitJavascript Problem Overview
I was experimenting on using Node version 6.2.1 with some of my code. Had plans to migrate most of the hyper-callback oriented codes to something that looks cleaner and maybe performs better.
I have no clue why, the terminal throws up an error when I try to execute the node code.
helloz.js
(async function testingAsyncAwait() {
await console.log("Print me!");
})();
Logs-
BOZZMOB-M-T0HZ:rest bozzmob$ node helloz.js
/Users/bozzmob/Documents/work/nextgennms/rest/helloz.js:1
(function (exports, require, module, __filename, __dirname) { (async function testingAsyncAwait() {
^^^^^^^^
SyntaxError: Unexpected token function
at Object.exports.runInThisContext (vm.js:53:16)
at Module._compile (module.js:513:28)
at Object.Module._extensions..js (module.js:550:10)
at Module.load (module.js:458:32)
at tryModuleLoad (module.js:417:12)
at Function.Module._load (module.js:409:3)
at Function.Module.runMain (module.js:575:10)
at startup (node.js:160:18)
at node.js:456:3
BOZZMOB-M-T0HZ:rest bozzmob$ node -v
v6.2.1
What am I missing? Please throw me some light on the same.
Update 1:
I tried to use Babel as Quentin suggested, But, I am getting the following error still.
Updated Code-
require("babel-core/register");
require("babel-polyfill");
(async function testingAsyncAwait() {
await console.log("Print me!");
})();
Logs-
BOZZMOB-M-T0HZ:rest bozzmob$ babel helloz.js > helloz.trans.js
SyntaxError: helloz.js: Unexpected token (3:7)
1 | require("babel-polyfill");
2 |
> 3 | (async function testingAsyncAwait() {
| ^
4 | await console.log("Print me!");
5 | })();
Javascript Solutions
Solution 1 - Javascript
Async functions are not supported by Node versions older than version 7.6.
You'll need to transpile your code (e.g. using Babel) to a version of JS that Node understands if you are using an older version.
That said, versions of Node.js which don’t support async functions are now all past End Of Life and are unsupported, so if you are using an earlier version you should very strongly consider upgrading.
Solution 2 - Javascript
Nodejs supports async/await from version 7.6.
Release post: https://v8project.blogspot.com.br/2016/10/v8-release-55.html
Solution 3 - Javascript
Node.JS does not fully support ES6 currently, so you can either use asyncawait module or transpile it using Babel.
install
npm install --save asyncawait
helloz.js
var async = require('asyncawait/async');
var await = require('asyncawait/await');
(async (function testingAsyncAwait() {
await (console.log("Print me!"));
}))();
Solution 4 - Javascript
If you are just experimenting you can use babel-node
command line tool to try out the new JavaScript features
- Install
babel-cli
into your project
$ npm install --save-dev babel-cli
- Install the presets
$ npm install --save-dev babel-preset-es2015 babel-preset-es2017
- Setup your babel presets
Create .babelrc
in the project root folder with the following contents:
{ "presets": ["es2015","es2017"] }
- Run your script with
babel-node
$ babel-node helloz.js
This is only for development and testing but that seems to be what you are doing. In the end you'll want to set up webpack (or something similar) to transpile all your code for production
- babel-node sample code : https://github.com/stujo/javascript-async-await/tree/15abac
If you want to run the code somewhere else, webpack can help and here is the simplest configuration I could work out:
- Full webpack example : https://github.com/stujo/javascript-async-await
Solution 5 - Javascript
node v6.6.0
If you just use in development. You can do this:
npm i babel-cli babel-plugin-transform-async-to-generator babel-polyfill --save-dev
the package.json
would be like this:
"devDependencies": {
"babel-cli": "^6.18.0",
"babel-plugin-transform-async-to-generator": "^6.16.0",
"babel-polyfill": "^6.20.0"
}
create .babelrc
file and write this:
{
"plugins": ["transform-async-to-generator"]
}
and then, run your async/await
script like this:
./node_modules/.bin/babel-node script.js
Solution 6 - Javascript
Though I'm coming in late, what worked for me was to install transform-async-generator and transform-runtime plugin like so:
npm i babel-plugin-transform-async-to-generator babel-plugin-transform-runtime --save-dev
the package.json
would be like this:
"devDependencies": {
"babel-plugin-transform-async-to-generator": "6.24.1",
"babel-plugin-transform-runtime": "6.23.0"
}
create .babelrc
file and write this:
{
"plugins": ["transform-async-to-generator",
["transform-runtime", {
"polyfill": false,
"regenerator": true
}]
]
}
and then happy coding with async/await
Solution 7 - Javascript
include and specify the node engine version to the latest, say at this time I did add version 8.
{
"name": "functions",
"dependencies": {
"firebase-admin": "~7.3.0",
"firebase-functions": "^2.2.1",
},
"engines": {
"node": "8"
},
"private": true
}
in the following file
> package.json