I have tons of files where I have to add this function.
const Media = require("../../functions/Media");
Media(....);
Is there any way to:
Directly add Media() function without requiring the file
Try declaring it as global in index file:
const {Media} = require('./functions/Media');
global.MediaGlobal = function Media(input) {
Media(input)
}
It really depends on the framework you are using. You need to find the starting index file and append all global functions there. Samples are given below.
// Override Globals in Backend Nodejs
if (typeof global !== "undefined") {
global.someGlobalFunction = function () {};
}
// Override Globals in Frontend Nodejs/reactjs
// Override Globals in Frontend javascript written on nodejs
if (typeof window !== "undefined") {
window.someGlobalFunction = function () {};
}
Node.js + Express (Backend)
Look for file define server, app.listen, Defined on top before import other modules
Node.js + React (Frontend)
Look for file define react.render, app.jsx, Defined on top before import other modules
Learn the concept of polyfill:
Best way to polyfill ES6 features in React app that uses create-react-app
Hi I am doing some research on RxJS. I am able to use the library simply by referencing it in my browser as such:
<script src="https://unpkg.com/#reactivex/rxjs#5.5.6/dist/global/Rx.js"></script>
It imports with the global object namespace variable of 'Rx'. I can make observables and do all the fun stuff.
Where everything breaks down is when I change the src to point to the latest UMD file like this <script src="https://unpkg.com/rxjs/bundles/rxjs.umd.js"></script>
The import seems to not be working as exported object functions don't seem to exist?
There is a specific function I am trying to use called 'fromEvent' that allows an observable to be created from any DOM event.
I am getting an error when using the latest RxJS 6.2.2 UMD file.
Why is this? If you look inside the js file at the bottom you can see the export of the function and at the top of the file you see the global namespace called 'rxjs'.
I am not using any loaders like requirejs nor do I have any experimental browser features enabled. I am not using any 'import' statements.
I am simply trying to reference the global namespace of the script object. The syntax for the module definition is identical except for Rx vs rxjs.
To replicate the error, simply create an Observable.fromEvent(.... and watch the error console.
Thanks!
Here's a oneliner to import UMD modules using browser modules and dynamic imports in 2020.
export default async (url, module = {exports:{}}) =>
(Function('module', 'exports', await (await fetch(url)).text()).call(module, module, module.exports), module).exports
Usage example:
const ednToJS = await importUMD(`https://unpkg.com/edn-to-js#0.1.2/dist/main.js`)
const rxjs = await importUMD('https://unpkg.com/rxjs#6.6.3/bundles/rxjs.umd.js')
tada
Recently the UMD bundle was renamed to just rxjs, see https://github.com/ReactiveX/rxjs/commit/556c904ea61a8424e5d24f170b20eadbc05d01f0#diff-6d2911fe563068b8126098588db98a84
If you want to use RxJS 6 you need to switch to "pipable" operators (and creation functions), see https://github.com/ReactiveX/rxjs/blob/master/docs_app/content/guide/v6/migration.md#operator-pipe-syntax
So for example this works:
<script src="https://unpkg.com/rxjs/bundles/rxjs.umd.js"></script>
<script>
rxjs.fromEvent(document, 'click').subscribe(console.log);
</script>
Demo: https://stackblitz.com/edit/rxjs6-demo-r2rtbz?file=index.html
export default async function (url, module = {exports:{}})
{
const response = await fetch(url);
const script = await response.text();
const func = Function("module", "exports", script)
func.call(module, module, module.exports);
return module.exports;
};
Same code reformatted
Here is an example after doing the proper import , note the pipe.
submission = rxjs.fromEvent($('#mybutton'), 'click')
.pipe(rxjs.operators.map((event) => {
return "something"
}));
I may rename the globals to 'r' and 'ro' to avoid the new verbosity.
Also bonus points if someone can point to piped error handling in 6.0!
It imports with the global object namespace variable of 'Rx'.
Maybe version 5.5.6 does but the latest version which you're trying to use, 6.2.2, does not. The object it exports to the global namespace is called rxjs. If you load https://unpkg.com/rxjs/bundles/rxjs.umd.js in a browser you'll see this in the source in the UMD module definition:
(function (global, factory) {
typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
typeof define === 'function' && define.amd ? define(['exports'], factory):
(factory((global.rxjs = global.rxjs || {})));
}(this, (function (exports) { 'use strict'; // etc
If you want to use fromEvent you can do so via rxjs.fromEvent.
To import any umd module from unpkg or jsdeliver in the browser with JavaScript, what I find mostly useful was using d3#require. Since actually importing the umd modules give me a bare "Module" object.
In your case it would work like this, notice I dont actually use any HTML, as a bonus this would also work for deno
import("https://raw.githack.com/d3/d3-require/main/src/index.mjs")
.then(
_=>_.require("https://unpkg.com/#reactivex/rxjs#5.5.6/dist/global/Rx.js")
)
.then(Object.keys)
.then(console.log)
Now, here I show an use case of require, where I require 2 modules, one is the Rx library, and the other is just an inspector library that shows off elements as if it were in the console
import("https://raw.githack.com/d3/d3-require/main/src/index.mjs").then(async _=>{
var inspector=await _.require("#observablehq/inspector");
var Rx=_.require("https://unpkg.com/#reactivex/rxjs#5.5.6/dist/global/Rx.js");
var x=new inspector.Inspector(window.inspect);
x.fulfilled(await Rx)
return x;
})
#import url("https://raw.githack.com/observablehq/inspector/main/src/style.css")
<div id="inspect" />
I have an external JS library with a global parameter:
function Thing() { ... }
...
var thing = new Thing();
There is a TypeScript definition file, so in thing.d.ts:
declare var thing: ThingStatic;
export default thing;
export interface ThingStatic {
functionOnThing(): ThingFoo;
}
export interface ThingFoo {
... and so on
Then I import this into my own TS files with:
import thing from 'thing';
import {ThingFoo} from 'thing';
...
const x:ThingFoo = thing.functionOnThing();
The problem is that transpiles to:
const thing_1 = require("thing");
...
thing_1.default.functionOnThing();
Which throws an error. I've asked about that in another question, and the suggestion is to use:
import * as thing from 'thing';
That doesn't fix it - it gives me thing.default in TS but then that's undefined once transpiled to JS.
I think there's something wrong with thing.d.ts - there must be a way to define a typed global parameter that can be imported.
How should I write thing.d.ts so that it represents the JS correctly and doesn't transpile to include default or other properties not actually present?
If the only way to use that library is by accessing its globals (as opposed to importing it as node module or amd or umd module), then the easiest way to go is have a declaration file without any exports at top level. Just declaring a variable is enough. To use it, you have to include that declaration file when compiling your typescript code, either by adding it to files or include in tsconfig.json, or directly on command line. You also have to include the library with a <script> tag at runtime.
Example: thing.d.ts
declare var thing: ThingStatic;
declare interface ThingStatic {
functionOnThing(): ThingFoo;
}
declare interface ThingFoo {
}
test-thing.ts
const x:ThingFoo = thing.functionOnThing();
can be compiled together
./node_modules/.bin/tsc test-thing.ts thing.d.ts
the result in test-thing.js:
var x = thing.functionOnThing();
See also this question about ambient declarations.
Note: there are module loaders out there that allow using global libraries as if they were modules, so it's possible to use import statement instead of <script> tag, but how to configure these module loaders to do that is another, more complicated question.
I'm writing a browser api with es6 (translated with babel). Since other js are going to call my api, I need to make my api accessible from the global (window) scope.
With module pattern in plain js (es5) I would have done something like this:
myApp.js
var myApp = (function(){
var a, b, c;
function setA(){
// set a
}
// other functions
return {
"setA": setA,
// ... other functions
};
}());
myAppExt.js
window.myApp = window.myApp || {};
(function(app){
app.Module1 = (function(){
return {
// methods of this module
};
}());
}(myApp));
With es6 we're not supposed to do something like this but to achieve the same objective I'm writing my app in this way:
myApp.js
import method1 from './common/module1.js'
import init from './folder/init.js'
import {method2, method3} from './folder/module2.js'
import log from './common/log.js'
const myApp = {};
window.myApp = myApp;
myApp.method1 = method1;
myApp.method2 = method2;
myApp.method3 = method3;
myApp.log = log;
init();
Is this the best way to achieve this goal or is there any better design solution?
If you are going to develop a library you will probably end up generating one single bundled file which contains all the contents of your library. To create a a a bundle you need a tool like webpack or browserify, both tools allow you to create your library in a way that can be consumed in many ways (AMD, CommonJS, global...).
So you need to create a root module:
myLibrary.js
import something from './framework/module1.js';
import somethingElse from './framework/module2.js';
// export public parts of your library
export {something};
export {somethingElse };
Then use webpack library setting:
{
output: {
// export itself to a global var
libraryTarget: "var",
// name of the global var: "Foo"
library: "Foo"
},
externals: {
// require("jquery") is external and available
// on the global var jQuery
"jquery": "jQuery"
}
}
More info here.
You can also use browserify standalone setting:
--standalone -s Generate a UMD bundle for the supplied export name.
This bundle works with other module systems and sets the name
given as a window global if no module system is found.
More info here.
I've actually merged the solution proposed from OweR ReLoaDeD with another I've found.
After configuring webpack to export global variable, instead of importing and then exporting methods I've exported directly what I needed to be available in the public api.
export {method} from './common/file1.js';
export * from './dir/file2.js'
export {anothermethod} from './common/file2.js
Thank you for the help
What is the purpose of Node.js module.exports and how do you use it?
I can't seem to find any information on this, but it appears to be a rather important part of Node.js as I often see it in source code.
According to the Node.js documentation:
module
A reference to the current
module. In particular module.exports
is the same as the exports object. See
src/node.js for more information.
But this doesn't really help.
What exactly does module.exports do, and what would a simple example be?
module.exports is the object that's actually returned as the result of a require call.
The exports variable is initially set to that same object (i.e. it's a shorthand "alias"), so in the module code you would usually write something like this:
let myFunc1 = function() { ... };
let myFunc2 = function() { ... };
exports.myFunc1 = myFunc1;
exports.myFunc2 = myFunc2;
to export (or "expose") the internally scoped functions myFunc1 and myFunc2.
And in the calling code you would use:
const m = require('./mymodule');
m.myFunc1();
where the last line shows how the result of require is (usually) just a plain object whose properties may be accessed.
NB: if you overwrite exports then it will no longer refer to module.exports. So if you wish to assign a new object (or a function reference) to exports then you should also assign that new object to module.exports
It's worth noting that the name added to the exports object does not have to be the same as the module's internally scoped name for the value that you're adding, so you could have:
let myVeryLongInternalName = function() { ... };
exports.shortName = myVeryLongInternalName;
// add other objects, functions, as required
followed by:
const m = require('./mymodule');
m.shortName(); // invokes module.myVeryLongInternalName
This has already been answered but I wanted to add some clarification...
You can use both exports and module.exports to import code into your application like this:
var mycode = require('./path/to/mycode');
The basic use case you'll see (e.g. in ExpressJS example code) is that you set properties on the exports object in a .js file that you then import using require()
So in a simple counting example, you could have:
(counter.js):
var count = 1;
exports.increment = function() {
count++;
};
exports.getCount = function() {
return count;
};
... then in your application (web.js, or really any other .js file):
var counting = require('./counter.js');
console.log(counting.getCount()); // 1
counting.increment();
console.log(counting.getCount()); // 2
In simple terms, you can think of required files as functions that return a single object, and you can add properties (strings, numbers, arrays, functions, anything) to the object that's returned by setting them on exports.
Sometimes you'll want the object returned from a require() call to be a function you can call, rather than just an object with properties. In that case you need to also set module.exports, like this:
(sayhello.js):
module.exports = exports = function() {
console.log("Hello World!");
};
(app.js):
var sayHello = require('./sayhello.js');
sayHello(); // "Hello World!"
The difference between exports and module.exports is explained better in this answer here.
Note that the NodeJS module mechanism is based on CommonJS modules which are supported in many other implementations like RequireJS, but also SproutCore, CouchDB, Wakanda, OrientDB, ArangoDB, RingoJS, TeaJS, SilkJS, curl.js, or even Adobe Photoshop (via PSLib).
You can find the full list of known implementations here.
Unless your module use node specific features or module, I highly encourage you then using exports instead of module.exports which is not part of the CommonJS standard, and then mostly not supported by other implementations.
Another NodeJS specific feature is when you assign a reference to a new object to exports instead of just adding properties and methods to it like in the last example provided by Jed Watson in this thread. I would personally discourage this practice as this breaks the circular reference support of the CommonJS modules mechanism. It is then not supported by all implementations and Jed example should then be written this way (or a similar one) to provide a more universal module:
(sayhello.js):
exports.run = function() {
console.log("Hello World!");
}
(app.js):
var sayHello = require('./sayhello');
sayHello.run(); // "Hello World!"
Or using ES6 features
(sayhello.js):
Object.assign(exports, {
// Put all your public API here
sayhello() {
console.log("Hello World!");
}
});
(app.js):
const { sayHello } = require('./sayhello');
sayHello(); // "Hello World!"
PS: It looks like Appcelerator also implements CommonJS modules, but without the circular reference support (see: Appcelerator and CommonJS modules (caching and circular references))
Some few things you must take care if you assign a reference to a new object to exports and /or modules.exports:
1. All properties/methods previously attached to the original exports or module.exports are of course lost because the exported object will now reference another new one
This one is obvious, but if you add an exported method at the beginning of an existing module, be sure the native exported object is not referencing another object at the end
exports.method1 = function () {}; // exposed to the original exported object
exports.method2 = function () {}; // exposed to the original exported object
module.exports.method3 = function () {}; // exposed with method1 & method2
var otherAPI = {
// some properties and/or methods
}
exports = otherAPI; // replace the original API (works also with module.exports)
2. In case one of exports or module.exports reference a new value, they don't reference to the same object any more
exports = function AConstructor() {}; // override the original exported object
exports.method2 = function () {}; // exposed to the new exported object
// method added to the original exports object which not exposed any more
module.exports.method3 = function () {};
3. Tricky consequence. If you change the reference to both exports and module.exports, hard to say which API is exposed (it looks like module.exports wins)
// override the original exported object
module.exports = function AConstructor() {};
// try to override the original exported object
// but module.exports will be exposed instead
exports = function AnotherConstructor() {};
the module.exports property or the exports object allows a module to select what should be shared with the application
I have a video on module_export available here
When dividing your program code over multiple files, module.exports is used to publish variables and functions to the consumer of a module. The require() call in your source file is replaced with corresponding module.exports loaded from the module.
Remember when writing modules
Module loads are cached, only initial call evaluates JavaScript.
It's possible to use local variables and functions inside a module, not everything needs to be exported.
The module.exports object is also available as exports shorthand. But when returning a sole function, always use module.exports.
According to: "Modules Part 2 - Writing modules".
the refer link is like this:
exports = module.exports = function(){
//....
}
the properties of exports or module.exports ,such as functions or variables , will be exposed outside
there is something you must pay more attention : don't override exports .
why ?
because exports just the reference of module.exports , you can add the properties onto the exports ,but if you override the exports , the reference link will be broken .
good example :
exports.name = 'william';
exports.getName = function(){
console.log(this.name);
}
bad example :
exports = 'william';
exports = function(){
//...
}
If you just want to exposed only one function or variable , like this:
// test.js
var name = 'william';
module.exports = function(){
console.log(name);
}
// index.js
var test = require('./test');
test();
this module only exposed one function and the property of name is private for the outside .
There are some default or existing modules in node.js when you download and install node.js like http, sys etc.
Since they are already in node.js, when we want to use these modules we basically do like import modules, but why? because they are already present in the node.js. Importing is like taking them from node.js and putting them into your program. And then using them.
Whereas Exports is exactly the opposite, you are creating the module you want, let's say the module addition.js and putting that module into the node.js, you do it by exporting it.
Before I write anything here, remember, module.exports.additionTwo is same as exports.additionTwo
Huh, so that's the reason, we do like
exports.additionTwo = function(x)
{return x+2;};
Be careful with the path
Lets say you have created an addition.js module,
exports.additionTwo = function(x){
return x + 2;
};
When you run this on your NODE.JS command prompt:
node
var run = require('addition.js');
This will error out saying
Error: Cannot find module addition.js
This is because the node.js process is unable the addition.js since we didn't mention the path. So, we have can set the path by using NODE_PATH
set NODE_PATH = path/to/your/additon.js
Now, this should run successfully without any errors!!
One more thing, you can also run the addition.js file by not setting the NODE_PATH, back to your nodejs command prompt:
node
var run = require('./addition.js');
Since we are providing the path here by saying it's in the current directory ./ this should also run successfully.
A module encapsulates related code into a single unit of code. When creating a module, this can be interpreted as moving all related functions into a file.
Suppose there is a file Hello.js which include two functions
sayHelloInEnglish = function() {
return "Hello";
};
sayHelloInSpanish = function() {
return "Hola";
};
We write a function only when utility of the code is more than one call.
Suppose we want to increase utility of the function to a different file say World.js,in this case exporting a file comes into picture which can be obtained by module.exports.
You can just export both the function by the code given below
var anyVariable={
sayHelloInEnglish = function() {
return "Hello";
};
sayHelloInSpanish = function() {
return "Hola";
};
}
module.export=anyVariable;
Now you just need to require the file name into World.js inorder to use those functions
var world= require("./hello.js");
The intent is:
Modular programming is a software design technique that emphasizes
separating the functionality of a program into independent,
interchangeable modules, such that each contains everything necessary
to execute only one aspect of the desired functionality.
Wikipedia
I imagine it becomes difficult to write a large programs without modular / reusable code. In nodejs we can create modular programs utilising module.exports defining what we expose and compose our program with require.
Try this example:
fileLog.js
function log(string) { require('fs').appendFileSync('log.txt',string); }
module.exports = log;
stdoutLog.js
function log(string) { console.log(string); }
module.exports = log;
program.js
const log = require('./stdoutLog.js')
log('hello world!');
execute
$ node program.js
hello world!
Now try swapping ./stdoutLog.js for ./fileLog.js.
What is the purpose of a module system?
It accomplishes the following things:
Keeps our files from bloating to really big sizes. Having files with e.g. 5000 lines of code in it are usually real hard to deal with during development.
Enforces separation of concerns. Having our code split up into multiple files allows us to have appropriate file names for every file. This way we can easily identify what every module does and where to find it (assuming we made a logical directory structure which is still your responsibility).
Having modules makes it easier to find certain parts of code which makes our code more maintainable.
How does it work?
NodejS uses the CommomJS module system which works in the following manner:
If a file wants to export something it has to declare it using module.export syntax
If a file wants to import something it has to declare it using require('file') syntax
Example:
test1.js
const test2 = require('./test2'); // returns the module.exports object of a file
test2.Func1(); // logs func1
test2.Func2(); // logs func2
test2.js
module.exports.Func1 = () => {console.log('func1')};
exports.Func2 = () => {console.log('func2')};
Other useful things to know:
Modules are getting cached. When you are loading the same module in 2 different files the module only has to be loaded once. The second time a require() is called on the same module the is pulled from the cache.
Modules are loaded in synchronous. This behavior is required, if it was asynchronous we couldn't access the object retrieved from require() right away.
ECMAScript modules - 2022
From Node 14.0 ECMAScript modules are no longer experimental and you can use them instead of classic Node's CommonJS modules.
ECMAScript modules are the official standard format to package JavaScript code for reuse. Modules are defined using a variety of import and export statements.
You can define an ES module that exports a function:
// my-fun.mjs
function myFun(num) {
// do something
}
export { myFun };
Then, you can import the exported function from my-fun.mjs:
// app.mjs
import { myFun } from './my-fun.mjs';
myFun();
.mjs is the default extension for Node.js ECMAScript modules.
But you can configure the default modules extension to lookup when resolving modules using the package.json "type" field, or the --input-type flag in the CLI.
Recent versions of Node.js fully supports both ECMAScript and CommonJS modules. Moreover, it provides interoperability between them.
module.exports
ECMAScript and CommonJS modules have many differences but the most relevant difference - to this question - is that there are no more requires, no more exports, no more module.exports
In most cases, the ES module import can be used to load CommonJS modules.
If needed, a require function can be constructed within an ES module using module.createRequire().
ECMAScript modules releases history
Release
Changes
v15.3.0, v14.17.0, v12.22.0
Stabilized modules implementation
v14.13.0, v12.20.0
Support for detection of CommonJS named exports
v14.0.0, v13.14.0, v12.20.0
Remove experimental modules warning
v13.2.0, v12.17.0
Loading ECMAScript modules no longer requires a command-line flag
v12.0.0
Add support for ES modules using .js file extension via package.json "type" field
v8.5.0
Added initial ES modules implementation
You can find all the changelogs in Node.js repository
let test = function() {
return "Hello world"
};
exports.test = test;