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tactonbishop 2022-08-01 19:30:05 +01:00
parent f7311789a7
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2
Operating_Systems/Disks/Swap_space.md
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@ -35,4 +35,4 @@ You will want the swap to be activated every time the OS boots so add the follow
## Create a swap file ## Create a swap file
// TODO: Add info // TODO: Add info here

57
Programming_Languages/NodeJS/Modules/Modules.md
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@ -6,9 +6,9 @@ tags:
- node-modules - node-modules
--- ---
# Modules
> > Modules are partitioned files where we define our variables and functions. Values defined in modules are scoped to that specific module, constituting a unique name space. This avoids name clashes in large programs.
> Modules are small files where we define our variables and functions. Values defined in modules are scoped to that specific module, constituting a unique name space. This avoids name clashes in large programs.
* Every file in a Node application is considered a module. * Every file in a Node application is considered a module.
@ -20,15 +20,13 @@ tags:
Node keeps an internal record of the properties of a module. To see this we can log the property `module` to the console. Node keeps an internal record of the properties of a module. To see this we can log the property `module` to the console.
````js ```js
// index.js // index.js
console.log(module) console.log(module)
```
````
This gives us: This gives us:
````json ```plaintext
Module { Module {
 id: '.',  id: '.',
 path: '/home/thomas/repos/node-learning',  path: '/home/thomas/repos/node-learning',
@ -44,8 +42,7 @@ Module {
   '/node_modules'    '/node_modules'
 ]  ]
} }
```` ```
## Exports ## Exports
* Whenever we export a property or method from a module we are directly targeting the `exports` property of the module object. * Whenever we export a property or method from a module we are directly targeting the `exports` property of the module object.
@ -131,61 +128,31 @@ Here the thing exported could be a composite function or an object that basicall
*Export a composite single function* *Export a composite single function*
````js ```js
module.exports = () => { module.exports = () => {
foo() {...} foo() {...}
bar() {...} bar() {...}
} }
```
````
*Export an object* *Export an object*
````js ```js
module.exports = { module.exports = {
foo : () => {...}, foo : () => {...},
bar: () => {...} bar: () => {...}
} }
```
````
**Both of these structures would be referred to in the same way when importing and using them** **Both of these structures would be referred to in the same way when importing and using them**
Or you could export an actual class as the default. This is practically the same as the two above other than that you would have to use `new` to initiate an instance of the class. Or you could export an actual class as the default. This is practically the same as the two above other than that you would have to use `new` to initiate an instance of the class.
````js ```js
export default class { export default class {
foo() {} foo() {}
bar() {} bar() {}
} }
```` ```
## Built-in modules
Node has numerous built-in methods that provide helpful utility methods:
* [File system module](File%20system%20module.md)
* [Events module](Events%20module.md)
## Structure of Node module methods
Every method belonging to the in-built modules of Node has a callback structure: a callback function of which the first argument is an error-handler and the second is the (typically asynchronous) returned value.
For example
````js
fs.readdir('./', function(err, files) {
if (err) {
console.error(err)
} else {
console.log(files)
}
})
// ['files', 'that', 'were', 'returned']
````