"Uncaught ReferenceError: printMe is not defined" at onload method in HTML - javascript

I'm currently trying to get started using webpack and ran into "Uncaught ReferenceError: printMe is not defined" error when trying to call my "init" method from HTML using the onload tag despite exporting the methods. My files are as follows:
print.js (located in /resources/static):
export function printMe() {
console.log("Hi");
}
index.js (located in /resources/static):
import {printMe} from "./print";
export function component() {
const element = document.createElement('div');
const btn = document.createElement('button');
btn.innerHTML = 'Click me and check the console!';
btn.onclick = printMe;
element.appendChild(btn);
return element;
}
export function init() {
console.log("init ran");
}
document.body.appendChild(component());
webpack.config.js:
const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
module.exports = {
mode: 'development',
entry: {
index: './resources/static/index.js',
},
devtool: 'inline-source-map',
plugins: [
new HtmlWebpackPlugin({
title: 'Output Management',
}),
],
output: {
filename: '[name].bundle.js',
path: path.resolve(__dirname, 'dist'),
clean:true,
},
};
index.html (located in /dist):
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Output Management</title>
<meta name="viewport" content="width=device-width, initial-scale=1"><script defer src="index.bundle.js"></script></head>
<body onload="init()">
</body>
</html>
index.bundle.js (located in /dist) I'm not going to include this file as I don't believe it to be necessary to the solution, although is important to note that it is actually there. Any help is appreciated

Even though you say export, I think that webpack isn't including it in your bundle since you never use the function in the JavaScript code. You'll either need a plugin to monitor your HTML, or use addEventListener on the body to add an "onLoad" event handler.
The simplest way to do this is with the event listener (don't include parentheses after init; see Why is the method executed immediately when I use setTimeout?):
document.body.addEventListener('load', init);

Related

HTML error using functions from bundle.js

I've created a bundle.js file using webpack to organize all my javascript code. I was expecting to use it in my html file but having troubles using the function. An error always returns when I try to call the function index.html:9 Uncaught TypeError: App.testButton is not a function at setup.
I had the impression that if I configured the webpack with the library output specified, I would be able to access the functions via the specified library name.
What am I doing wrong?
App.js
import testButton from './testButton.js';
console.log("I'm the entry point");
testButton();
testButton.js
function testButton()
{
console.log("Test Button");
};
export default testButton;
index.html
<!DOCTYPE html>
<html lang="en">
<head>
<script src="dist/bundle.js"></script>
<script>
function setup()
{
console.log("Initializing a webpage");
App.testButton()
}
</script>
</head>
<body onload="setup();">
</body>
</html>
webpack.config.js
const path = require('path');
module.exports = {
entry: './app.js',
mode: 'development',
output: {
filename: 'bundle.js',
path: path.resolve(__dirname, 'dist'),
libraryTarget: 'var',
library: 'App'
},
};
I found this to work for me. I needed to modify App.js to include babel so I could use ES5 which allowed me to use require to populate module.exports.
App.js
require('babel-register')({
presets: ['env']
});
module.exports = {
testButton: require('./testButton.js'),
testButton2: require('./testButton2.js')
};
testButton.js
export function testButton()
{
console.log("Test Button");
};
testButton2.js
export function testButton()
{
console.log("Test Button 2");
};
index.html
function setup()
{
App.testButton.testButton();
App.testButton2.testButton();
}
</script>
Output in Console
Test Button
test Button 2

Unable to find Class reference from Webpack bundled file

I am pretty new to webpack and frontend development.
I have a JS file which has multiple classes, this classes would be used by other JS files.
The problem is when I directly add JS file in Script tag, and check in Browser console I can retrieve Class properly, but when I run Webpack and check with the bundled code i am unable to find any reference for the class
Following is the test code snippet:
main.js
class Human1 {
constructor(params) {
this.name = params.name
}
getName(){
console.log(`My name is ${this.name}`);
}
}
JS file used for webpack(created new JS so as to avoid class name re declaration)
class Human2 {
constructor(params) {
this.name = params.name
}
getName(){
console.log(`My name is ${this.name}`);
}
}
webpackConfig.js:
const path = require('path');
module.exports = {
entry: './human.js',
mode: 'none',
target: "web",
output: {
path: path.resolve(__dirname, 'dist'),
filename: 'bundle.js'
},
};
Index.html
<!DOCTYPE html>
<html>
<head>
<title>titlefdf</title>
</head>
<body>
<script type="text/javascript" src="./bundle.js"></script>
<script type="text/javascript" src="./main.js"></script>
<h2> Welcome </h2>
</body>
</html>
When the files are loaded in html. In the console window I get Human1 but for Human2 I get Uncaught ReferenceError: Human2 is not defined.
Any reason what am I doing wrong
You can do so by exposing it as Library. Here is the reference link

webpack compile javascript for browser

Thanks for your attention!
I have built a javascript file from my source code using webpack, I was mean to use it in brower, but it seems not working for me, so I post this for help
here is my project tree
project
├── dist
│   └── my-dist.js
├── index.js
├── lib
│   └── my-source.js
└── webpack.config.js
here is my-source.js
'use strict'
const somepackage = require("somepackage")
module.exports = MyPkg
function MyPkg(param) {
this.myprop = param
}
MyPkg.prototype.Afunc = function () {
consolg.log("hello from A ", this.myprop)
}
MyPkg.prototype.Bfunc = function (param) {
// B do some thing
}
here is my index.js
exports = module.exports = require('./lib/MyPkg');
here is my webpack.config.js
const path = require('path')
module.exports = {
entry: './index.js',
output: {
path: path.resolve(__dirname, 'dist'),
filename: 'my-dist.js'
},
module: {
rules: [{
test: /\.js$/,
exclude: /(node_modules|bower_components)/,
use: {
loader: 'babel-loader',
options: {
presets: ['babel-preset-env']
}
}
}]
}
}
then i run "webpack" to build the file, it seems ok, and the "my-dist.js" file was created, so i try to use it like this:
<html>
<head>
</head>
<body>
<div>
<button onclick="func()">click here</button>
</div>
</body>
<script src="dist/my-dist.js"></script>
<script>
var pkg = new MyPkg('haha')
function func() {
pkg.Afunc()
}
</script>
</html>
but it throw error like "Uncaught ReferenceError: MyPkg is not defined", and i really don't know how to fix it, please give my a hand, thank you guys~
Edit x2:
Here's a GitHub Repo with further explanations:
https://github.com/superjose/webpack-simple-example
If I recall correctly, I had this issue in the past. Webpack the JavaScript from your entry file so that no other file or code has direct access to it.
Therefore, in your index.html this will not work
<script>
var pkg = new MyPkg('haha')
function func() {
pkg.Afunc()
}
</script>
What you need to do is to use EventListeners so you can target the elements.
So you have this button: (Add a class or an id to better identify it)
<button onclick="func()" id="js-pkg">click here</button>
Then, inside index.js:
document.addEventListener('DOMContentLoaded', () => {
document.getElementById('js-pkg').addEventListener(MyPkg);
// This also works:
// document.querySelector('#js-pkg').addEventListener(MyPkg);
});
Note:
We add the 'DOMContentLoaded' event so we wait for the DOM to be loaded before making any operations. Not doing so, it may result in the button to be not defined, since it may not be parsed or rendered by the browser's engine
Edit: More detailed approach below
Suppose you have the following structure:
----index.html
----index.js
----Email/
---------email.js
----Validator/
---------validator.js
Whereas index.js is your main entry file (Where Webpack loads the JavaScript).
Email.js contents:
// Ficticious/non-existent npm package
import email from 'send-email'
// Custom and ficticious email class that will send emails
export class Email {
sendEmail(subject, message) {
// You would send the email somehow.
email.send('contact#support.com' this.subject, message);
}
}
Validator.js contents:
// Checks if the value is undefined or null
module.exports = function (value) {
return !!value
}
In your index.html:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<input type="name" id="js-name" placeholder="message" />
<textarea id="js-msg" placeholder="Write us a message"></textarea>
<button id="js-send">Send us a message!!</button>
<!-- Awful Real-life example -->
<button id="js-validate">Validate Text!</button>
<script src="index.js"></script>
</body>
</html>
In index.js (Webpack's main file):
// We import the email class that we want to use
import { Email } from './Email/email.js'
// We also add validator
import validator from './Validator/validator.js'
/**
* Now the actual magic. Webpack scopes the variable and function names, changing
* the normal values, in order (I could be wrong with this) to avoid collisions with other functions, and variables.
*
* Nonetheless, JavaScript allow us to programatically attach those functions to the element via event listeners.
* https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener
* This means that <input type="button" onclick="func()" /> the onclick() event is the same
* as element.addEventListener('click', func); Where element is the <input type="button" found via a document.getElementById/querySelector/querySelectorAll/getElementsByTagName/etc
* Therefore, even if Webpack scopes the variable and function names, we would be able to attach it since it resides inside Webpack's code.
* The first thing we do is to add a "DOMContentLoaded" event. This is similar to jQuery's $(document).ready(function() { }); We need for the HTML to be loaded in order for us to add the event listener. You didn't have that problem in the past because you would add it directly to the HTML.
**/
document.addEventListener('DOMContentLoaded', () => {
let sendEmail = document.getElementById('js-send');
let name = document.getElementById('js-name');
let email = new Email();
let validateBtn = document.getElementById('js-validate');
// We pass the functions without parenthesis.
// Note that validator is a function, while Email is a class.
// Email needs to be instantiated first, and then we assign
// the method that it calls.
validateBtn.addEventListener('click', validator);
sendEmail.addEventListener('click', email.sendEmail);
});
ok, just keep this in record.
I figure out a special way, here it's looks like:
the project tree is now looks like:
project
├── dist
│ └── my-dist.js
├── src
│ └── my-entry-build.js
├── index.js
├── lib
│ └── my-source.js
└── webpack.config.js
and I updated the "webpack.config.js" and the "my-entry-build.js", the others keep still
the new "webpack.config.js" is like:
const path = require('path')
module.exports = {
entry: './src/my-entry-build.js',
output: {
path: path.resolve(__dirname, 'dist'),
filename: 'my-dist.js'
},
module: {
rules: [{
test: /\.js$/,
exclude: /(node_modules|bower_components)/,
use: {
loader: 'babel-loader',
options: {
presets: ['babel-preset-env']
}
}
}]
}
}
the new "my-entry-build.js" is like:
const MyPkg = require('../index.js')
window.MyPkg = MyPkg
and everything done!

how can i get the lang html attribute in webpack configuration

const lang = "the lang html attribute value";
var languages = {
"fr": require("./languages/fr.json"),
"en": require("./languages/en.json")
};
var configuration = Object.keys(languages).map(function(language) {
const loadedLang = (lang.indexOf("fr") > -1) ? "fr" : "en";
return {
name: loadedLang,
entry: './assets/js/main.js',
output: {
filename: 'bundle.js',
path: path.resolve(__dirname, 'assets/js/dist')
},
plugins: [
new I18nPlugin(
languages[loadedLang]
)
]
}
});
So I am trying to get the <html lang="en-US"> lang attribute and I know that I have no access to the DOM from the webpack config file.
My question is:
Does someone have an idea about how to do this or how to have access to the local storage from webpack?
PS:
I tried a node-localstorage package but it doesn't do the job I want
An answer to your question would be to load the file with the fs api and then use an regex to extract your language:
const fs = require('fs');
const content = fs.readFileSync('PATH_TO_INDEX.HTML', options: { encoding: 'utf8' });
const lang = content.match(/<html lang="(.*)"/)[1];
But I would recommend to do it the "webpack" way:
Create a separate folder for every language, that contains the index.html and the js file specific to each language language.
For this, add the following:
output: {
path: path.resolve(__dirname, `assets/js/dist/${language}/`)
},
plugins: [
new HtmlWebpackPlugin({
template: 'PATH_TO_YOUR_TEMPLATE',
lang: language,
title: 'your page title',
})
]
Please don't forget to install the html-webpack-plugin and require it at the top of your config.
And create a new file index.html with the following content:
<!DOCTYPE html>
<html lang="<%= htmlWebpackPlugin.options.lang %>">
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8"/>
<title><%= htmlWebpackPlugin.options.title %></title>
</head>
<body>
</body>
</html>
So now for every language a separate index.html with the right language and the right js file for that language is created in every language folder.
So not the html file dictates the language set, but the webpack config.

Calling webpacked code from outside (HTML script tag)

Suppose that I have class like this (written in typescript) and I bundle it with webpack into bundle.js.
export class EntryPoint {
static run() {
...
}
}
In my index.html I will include the bundle, but then I would also like to call that static method.
<script src="build/bundle.js"></script>
<script>
window.onload = function() {
EntryPoint.run();
}
</script>
However, the EntryPoint is undefined in this case. How would I call the bundled javascript from another script then?
Added: Webpack config file.
It seems that you want to expose the webpack bundle as a library. You can configure webpack to expose your library in the global context within a variable of your own, like EntryPoint.
I don't know TypeScript so the example uses plain JavaScript instead. But the important piece here is the webpack configuration file, and specifically the output section:
webpack.config.js
module.exports = {
entry: './index.js',
output: {
path: './lib',
filename: 'yourlib.js',
libraryTarget: 'var',
library: 'EntryPoint'
}
};
index.js
module.exports = {
run: function () {
console.log('run from library');
}
};
Then you will be able to access your library methods like you expect:
<script src="lib/yourlib.js"></script>
<script>
window.onload = function () {
EntryPoint.run();
};
</script>
Check the gist with the actual code.
I managed to get this working without any further webpack.config.js modifications, by simply using the import statement which i called from my main/index.js file:
import EntryPoint from './EntryPoint.js';
window.EntryPoint = EntryPoint;
For reference, here's my weback.config.js file.
Initially I tried accomplishing the same using require, however it assigned the module wrapper to window.EntryPoint as opposed to the actual class.
In my circumstance I was able to call a function from within the bundled JavaScript from another script by writing the function to the window when creating it.
// In the bundled script:
function foo() {
var modal = document.createElement('div');
}
// Bind to the window
window.foo = foo;
// Then, in the other script where I want to reference the bundled function I just call it as a normal function
<button onClick="window.foo()">Click Me</button>
I wasn't able to use Babel so this worked for me.
I had a similar challenge, I wanted to create a bundle for multiple pages within a journey and wanted each page to have it's own entry point into the code, and without a separate bundle for each page.
Here's my approach, which is very similar to Kurt Williams but from a slightly different angle, also without changing webpack config:
JourneyMaster.js
import { getViewData } from './modules/common';
import { VIEW_DATA_API_URL } from './modules/constants';
import { createLandingPage, createAnotherPage } from './modules/components/pageBuilder';
window.landingPageInit = () => {
getViewData(VIEW_DATA_API_URL).then(viewData => {
createLandingPage(viewData);
});
};
window.anotherPageInit = () => {
getViewData(VIEW_DATA_API_URL).then(viewData => {
createAnotherPage(viewData);
});
};
// I appreciate the above could be one liners,
// but readable at a glance is important to me
Then an example of how I call these methods at the end of the html page:
<script src="/js/JourneyMaster.js"></script>
<script>window.landingPageInit();</script>
WEBPACK.CONFIG.JS
1.USING UMD
module.exports={
mode:'development',
entry:'./yourentry.js',
output:{
path:path.resolve(__dirname,"dist"),
filename:'main.js',
publicPath:'/dist/',
libraryTarget:'umd',
library:'rstate',
umdNamedDefine: true,
libraryExport: 'default'
}
}
index.html
<script src="dist/main.js"></script>
<script>
window.onload = function () {
rstate()=>{}
</script>
main.js
export default function rstate(){
console.log("i called from html")
}
2.USING VAR
module.exports={
mode:'development',
entry:'./yourentry.js',
output:{
path:path.resolve(__dirname,"dist"),
filename:'main.js',
publicPath:'/dist/',
libraryTarget:'var',
library: 'EntryPoint'
}
}
index.html
<script>
window.onload = function () {
EntryPoint.rstate()=>{}
</script>
main.js
module.exports={
rstate=function(){
console.log("hi module")
}
}
3.USING AMD as library we use like(for those who want to make lib)
define(['jquery', './aux-lib.js'], function ($) { ..(1).. });
Many of the answers so far work, it would only be necessary to clarify that Webpack will not recognize the library until it is built once declared.
You should use npm run build right after creating your library,
before continuing to work with npm start.
At least that's how it works for me, using only webpack.
Maybe this is some impostor syndrome on my part, but I think 'real' coders will cringe at my answer. Regardless, I found this solution to be the best fitting for being pragmatic about my time with my hobby project:
Chane your JS function declaration from:
function renderValue(value) {
to:
global.renderValue = function(value) {
Of course, you'll want to require('path/to/your_custom_js') as you would any file.
I found this answer here:
https://www.fastruby.io/blog/rails/webpack/from-sprockets-to-webpacker.html
This took me forever to figure out as the accepted answer wasn't working for me. Just make sure the function name is the same as the library in the config and it's bundled with the config specified -- npx webpack --config webpack.config.js --mode=development -- hopefully this saves people a few hours.
index.js (function to be bundled) >>
function EntryPoint() {
console.log('called from bundle');
}
module.exports = EntryPoint;
webpack.config.js >>
const path = require('path');
module.exports = {
entry: './src/index.js',
output: {
filename: 'main.js',
path: path.resolve(__dirname, 'dist'),
libraryTarget: 'var',
library: 'EntryPoint'
},
};
start.html (where the bundled function is called) >>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Azure SDK Storage Example</title>
<script type="text/javascript" src="./dist/main.js"></script>
</head>
<body>
<h1>Azure SDK Storage Example</h1>
</body>
</html>
<script>
EntryPoint();
</script>
App.ts:
namespace mytypescript.Pages {
export class Manage {
public Initialise() {
$("#btnNewActivity").click(() => {
alert("sdc'");
});
}
}
}
mypage.html:
<input class="button" type="button" id="btnNewActivity" value="Register New Activity" />
<script type="text/javascript">
var page = new mytypescript.Pages.Manage();
page.Initialise();
</script>

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