Can we add the same namespace for two javascript files? - javascript

I am trying to put all my javascript function in one namespace. I have two javascript files and i am trying to put all the functions both the files into one namespace. So when i define the same namespace for both the files. The first gets over written by the second. I have defined my namespace in both the files as shown below. Is there a way i can stop this other putting all the function to one file? Thanks for the help.
var mynamespace={
foo:function(){Som code},
bar:function(){some code}
};

Yes, you can. In each file:
var mynamespace = mynamespace || {};
And then pick the next line for the file you have:
mynamespace.foo = function () {
or
mynamespace.bar = function () {
Basically, what this does is assign a current value of mynamespace to mynamespace if it exists. Otherwise, it creates a new object. Note that depending on if you declare mynamespace above or not, you might need this line up top instead:
if (typeof mynamespace === 'undefined') { var mynamespace = {} }

Related

js - avoiding namespace conflict

Thus far I've worked only with relatively small projects (and mostly alone), but this time I have to collaborate with other programmers... basically because of that I must plan the structure of the website very carefully for the avoidance of spending hours debugging the code.
At this point I suppose doing that in the following manner. I divide my code in modules and store each module in a separate file inside an object (or a function) with a made-up name (lzheA, lzheB, lzheC etc.) to avoid conflicts whether an object with the same name was used in an another piece of code. When the document is loaded, I declare a variable (an object) that I use as a main namespace of the application. Properties of the object are the modules I defined before.
// file BI.lib.js
var lzheA = {
foo: function() {
},
bar: function() {
},
}
// file BI.init.js
function lzheK() {
BI.loadPage();
}
// file BI.loadPage.js
function lzheC() {
var result = document.getElementById('result');
result.innerHTML = "that worked";
}
// and so on
var lzheA,lzheB,lzheD,lzheE,lzheF,lzheG,lzheH,lzheI,lzheJ;
// doing the following when the document is loaded
var BI = {
lib: lzheA,
menu: lzheB,
loadPage: lzheC,
customScripts: lzheD,
_index: lzheE,
_briefs: lzheF,
_shop: lzheG,
_cases: lzheH,
_blog: lzheI,
_contacts: lzheJ,
init: lzheK,
}
BI.init();
https://jsfiddle.net/vwc2og57/2/
The question... is this way of structuring worth living or did I miss something because of lack of experience? Would the made-up names of the modules confuse you regardless of the fact that each one used only twice - while declaring the variable and assigning it to a property?
I consider the namespaces a good option when you want to modularize applications in Javascript. But I declare them in a different way
var myModule = myModule || {}; // This will allow to use the module in other places, declaring more than one specificComponent in other js file for example
myModule.specificComponent = (function(){
// Private things
var myVar = {};
var init = function() {
// Code
};
return {
init: init // Public Stuff
};
})();
If you want to call the init method, you would call it like this
myModule.specificComponent.init();
With this approach, i guarantee that the module will not be overwritten by another declaration in another place, and also I can declare internal components into my namespaces.
Also, the trick of just exposing what you want inside the return block, will make your component safer and you will be encapsulating your code in a pretty way.
Hope it helps

Global functions in javascript

I'm new to js and trying to understand global and private functions. I understand global and local variables. But if I have an html named test.html and a 2 js files named test1.js and test2.js. Now I include the test1.js and test2.js in test.html and call the functions written in test2.js inside test1.js and test.html.
The functions that I have written in test2.js are in this form
function abc(){...}
function pqr(){...} etc.
are these above functions global? If they are , how can I not make them global and still access them in test1.js and test.html?
As I have read global functions or global variables are bad right?
Everything in JS is bound to containing scope. Therefore, if you define a function directly in file, it will be bound to window object, i.e. it will be global.
To make it "private", you have to create an object, which will contain these functions. You are correct that littering global scope is bad, but you have to put something in global scope to be able to access it, JS libraries do the same and there is no other workaround. But think about what you put in global scope, a single object should be more than enough for your "library".
Example:
MyObject = {
abc: function(...) {...},
pqr: function(...) {...}
// other functions...
}
To call abc for somewhere, be it same file or another file:
MyObject.abc(...);
in test2.js you can write this to make the function global
window.abc = function(){...}
and then in test1.js yo can access it like this
window.parent.abc();
I hope it will help you
Anything defined in a file without any sort of wrapper will be bound to the window object. Anything bound to the window object is global.
Example:
//these are global variables
foo = 123;
var ABC = 'school';
//these are "private" variables
test = function(){
var foo = 123
}
(function(){
var ABC = 'school';
}).call(this);
Since global variables in every file will be part of the window object, you can access them between files. It is important when creating "private" variables you add var. This says override any global variables in the current "wrapper". If I have a global variable foo and I define it again in a function with var they will be separate.
var foo = 123;
(function(){
var foo = 987; //this foo is separate from the above foo
}).call(this);
If you do have a "wrapper" and you want to define a global function you can do it like this:
window.foo = 123;
(function(){
window.foo = 123;
}).call(this);
Both functions will do the same thing.
Personally, I prefer to put everything in a wrapper and only define global variables when I need them using window.
(function(){
//all code goes here
//define global variable
window.foo = 123;
})call(this);
var SomeName = function() {
var function1 = function (number) {
return number+1;
}
var anotherFunction = function (number) {
return number+2;
}
return {
function1: function (number) {
return function1(number);
},
function2: function (number) {
return anotherFunction(number);
}
}
}();
calling
console.log(SomeName.function1(1)); //logs 2
console.log(SomeName.function2(1)); //logs 3
A modern approach (2020) to using global data is by using a global object literal and define there all your needed logic.
const Website = {
foo () {
console.log('foo')
},
bar () {
console.log('bar')
}
}
document.addEventListener('DOMContentLoaded', () => {
Website.foo()
Website.bar()
})
If your code is more complex than a couple of lines you will need to separate your code into multiple files and with webpack you merge them together into one file.
import Foo from './js/Foo.js'
import Bar from './js/Bar.js'
// define here another object literal or setup document events.
// webpack will merge all this together into one file
<script src="js/webpack-merged.js"></script>
The reasons you don't want to import individual js files with html is described here. The jist of it is you will have poor performance, so you must bundle all your js.
If you don't understand why global variables are bad, then why are you trying to avoid them?
Global functions aren't necessarily bad. What's bad is state that anyone and anything and change.
In general since you're new to Javascript, it's fine to start out with global functions spread out across multiple javascript files that you include in your html file via script tags.
As you transition from beginner to intermediate, you will have to look into some "module" solution (I personally recommend RequireJS).
For now though, you can make do with a simpler module pattern:
var T1 = function() {
return < some module object >
})(); // notice the parenthesis
Google "Javascript module pattern".
Also see this answer.
vos fonctions ne sont pas global si vous faite l'erreur de les incorporé dans par exemple :
$( document ).ready(function() {
function myglobalfunction() { ... }
});
vous devez retirer
$( document ).ready(function() {
your functions are not global if you make the mistake of embedded them in for example:
$(document) .ready (function () {
function myglobalfunction () {
...
}
});
you must remove
$ (document) .ready (function () {

Proper use of RequireJS, Coffeescript and Revealing Module Pattern

I have defined the following piece of Coffeescript code below, which defines a function using RequireJS:
define 'PersonService', ['jquery'] ($) ->
getPerson = (id) ->
person = dataService.GetPerson id
{ getPerson: getPerson}
It produces the following:
(function() {
define('PersonService', ['jquery'](function($) {
var getPerson;
getPerson = function(id) {
var person;
return person = dataService.GetPerson(id);
};
return {
getPerson: getPerson
};
}));
}).call(this);
I guess the issue I have is with the self-executing function that is produced from the Coffeescript code. Will this cause issues that I am possibly not tracking? Or is this proper.
Thank you.
It's correct
The difference between not having a wrapped function and having one is to do with scope.
If you define var a = 10; in the global scope a becomes global with or without the var keyword.
When wrapped all variables are local to the wrapped function so do not end up global.
In you example everything is already wrapped in a function so yes you don't need the extra wrapping!
You can tell coffee-script not to add the wrapper function using
coffee -b, --bare compile without a top-level function wrapper
IMHO: It's better to always have the wrapper function so you don't need to think about it on a file to file basis.

Communication between scripts | Three methods

How do I properly communicate data betweens two scripts.
In this particular case I have an element in one script, but I want to append it in another script.
The simplest way I could do this is by using the global window object as go-between.
But globals are not best practice.
What is the correct way to pass this element to another script?
Both script are encapsulated in the module pattern.
Script 0 Create Element Point
var element = document.createElement( "div" );
element.innerHTML = response_text;
Script 1 Append Element Point
Vi.sta = {
// implemented in the boot loader - shared global space - appended child already - you don't have to append until now.
// Static data has already been composed.
// Pull off window and append or best practice
};
Both are encapsulated in the module pattern
(function(){
// the code here
})()
All JS scripts are run in the global scope. When the files are downloaded to the client, they are parsed in the global scope.
So if you've got
// File_1.js
var myObj = { colour : "blue" };
There's nothing stopping you from doing this:
// File_2.js
var otherObj = { colour : myObj.colour };
As long as File_1.js is loaded before File_2.js
If you are namespacing, ie: MYNAMESPACE = {}; and each file extends your namespace through modules (rather than "module pattern" referring to returning interfaces from immediately-invoking functions), then check for the module's existence.
If you ARE writing modules for a namespaced app, and you DO need access to variables from one module to another, then you should be providing an interface for that.
If you are SANDBOXING modules, then you need to provide them all a proxy similar to a service-locator or a "registry", or develop a messaging-system based on a mediator-pattern.
window.sharedSpace = {};
sharedSpace.sharedValue = 'foo bar';
That way you only have one global object instead of several.
Why don't you just pass the element to a function in the module?
var module1 = (function () {
return {
func1: function () {
// get your element
var someElement = ...;
// pass it to the other module
module2.func2(someElement);
}
};
}) ();
var module2 = (function () {
return {
func2: function (someElement) {
// do whatever you want with someElement
}
};
}) ();

My own mini-framework is not compatible with some projects

I failed to create a mini-library with some useful functions that I have found over the Internet, and I want to use them easily by just including a file to the HTML (like jQuery).
The problem is that some vars and functions share the same name and they are causing problems.
Is there a better solution to this instead of giving crazy names to the vars/funcs like "bbbb123" so the odds that someone is working with a "bbbb123" var is really low?
I would put all of your functions and variables into a single object for your library.
var MyLibrary = {
myFunc: function() {
//do stuff
},
myVar: "Foo"
}
There are a few different ways of defining 'classes' in JavaScript. Here is a nice page with 3 of them.
You should take one variable name in the global namespace that there are low odds of being used, and put everything else underneath it (in its own namespace).
For example, if I wanted to call my library AzureLib:
AzureLib = {
SortSomething: function(arr) {
// do some sorting
},
DoSomethingCool: function(item) {
// do something cool
}
};
// usage (in another JavaScript file or in an HTML <script> tag):
AzureLib.SortSomething(myArray);
Yes, you can create an object as a namespace. There are several ways to do this, syntax-wise, but the end result is approximately the same. Your object name should be the thing that no one else will have used.
var MyLibrary = {
myFunc: function() { /* stuff */ }
};
Just remember, it's object literal syntax, so you use label : value to put things inside it, and not var label = value;.
If you need to declare things first, use a wrapping function to enclose the environment and protect you from the global scope:
var MyLibrary = (function() {
var foo = 'bar';
return {
myFunc: function() { /* stuff */ }
};
})(); // execute this function right away to return your library object
You could put all of your library's functions inside of a single object. That way, as long as that object's name doesn't conflict, you will be good. Something like:
var yourLib = {};
yourLib.usefulFunction1 = function(){
..
};
yourLib.usefulFunction2 = function(){
..
};

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