I am new to AMD, and I've been wondering about how one can have a file like this, mixed functions and logic:
function abc() {
....
}
function def() {
....
}
function ghi() {
....
}
var something = { ... }
if (abc === something) {
for(var i = 1; i < 10000000; i++) {
...
}
}
... And so it goes on for 1200 lines or so.
So not everything in this file is inside functions, there is also just logic being executed outside functions.
How can I include a file like this in another module, and make sure all these functions and what not are NOT in the global namespace/scoped in AMD style?
You have to wrap entire file contents into a module definition:
define(function () {
function abc() {
// ....
}
function def() {
// ....
}
function ghi() {
// ....
}
var something = { /* ... */ }
if (abc === something) {
for(var i = 1; i < 10000000; i++) {
// ...
}
}
// ... And so it goes on for 1200 lines or so.
});
Then in the other module just require the thing from the above :) But none of those functions will be available to the module which needs the wrapped code. But that can also be sorted, just return them in the object literal at the end of the wrapped file
Related
I have two files: index.ts and A.ts
A.ts:
export default class {
do() {
console.log(someVar);
}
}
index.ts:
import A from './A';
function printIt(param) {
let someVar = param;
let a = new A();
a.do();
}
printIt('wow'); // Console output: wow
printIt('123'); // Console output: 123
Is it real to declare someVar for A.ts from index.ts without wrapping A class?
I know that Node.JS wrappes all modules in (function (exports, require, module, __filename, __dirname, process, global) { }: How to change the Node.js module wrapper?
I tried to make a custom require function and pass my var like an argument. But I don't understand how can I make own require function in TypScript. Are there any ideas?
The scope of variables depends on where they are defined, not where they are called. this is on purpose, so you do not accidentally call on variables you did not know about being in the same scope as your function's invocation.
You must explicitly tell the code you want to pass this new variable into it, either just like Lux showed, or through passing it to the function like:
export default class {
do(someVar) {
console.log(someVar);
}
}
function printIt(param) {
let someVar = param;
let a = new A();
a.do(someVar);
}
what you're trying to do is akin to having everything be a global variable.
if you MUST do this (you shouldn't), there is one way you can.
export default class {
do() {
console.log(global.someVar);
}
}
function printIt(param) {
global.someVar = param;
let a = new A();
a.do();
}
There's many reasons why you do not want to do global variables, here are some
Edits after clarification:
So the "this" keyword inside of a module refers to the module's global scope, so I tried the following snippet:
// modA.js
const moduleContext = this
class ExportedClass {
printer() {
console.log(moduleContext.someVar)
}
}
module.exports = { ExportedClass }
//modB.js
let A = require("./modA")
A.someVar = "hello world"
let obj = new A.ExportedClass()
obj.printer()
and it seems the context was removed, the same thing with ES6 imports using mjs files, what did Work however is this:
//modA.js
function printer() {
console.log(this.someVar)
}
module.exports = { printer }
//modB.js
let A = require("./modA")
A.someVar = "hello world"
A.printer()
it seems moduleContext points to the old module context object, and the new imported module has a different context object.
This still seems like a bad idea though, you're better off structuring your code so that you export a constructing function, that takes whatever needs to be "global" for that scope, and sets it inside.
What are you trying to do? The seperation for module is on purpose, so the scope of everything remains.
Next, you have a typo: it should probably be let a = new A(); not let a = new A;.
But why dont you just pass the variable as an argument to the constructor of your A class?
export default class {
someVar: string;
constructor(someVar) {
this.someVar = someVar;
}
do() {
console.log(this.someVar);
}
}
now you can just do
function printIt(param) {
let someVar = param;
let a = new A(someVar);
a.do();
}
I have NodeJS program.
In one class, I have various utility methods. One function, safeGithubPush, calls safeString, another func in the same class
module.exports = {
safeString(stringToCheck) {
console.log(validator.isAscii(stringToCheck), validator.matches(stringToCheck, /^((\w)*[-.]?(\w)*)*$/))
return (
validator.isAscii(stringToCheck) &&
validator.matches(stringToCheck, /^((\w)*[-.]?(\w)*)*$/)
);
},
safeGithubPush(currentJob) {
if (
!currentJob ||
!currentJob.payload ||
!currentJob.payload.repoName ||
!currentJob.payload.repoOwner ||
!currentJob.payload.branchName
) {
this.logIn(
currentJob,
`${' (sanitize)'.padEnd(15)}failed due to insufficient job definition`
);
throw invalidJobDef;
}
if (
this.safeString(currentJob.payload.repoName) &&
this.safeString(currentJob.payload.repoOwner) &&
this.safeString(currentJob.payload.branchName)
) {
return true;
}
throw invalidJobDef;
},
}
While this.logIn(), another func in the utility class, works just fine, I get the error for safeString:
Error caught by first catch: TypeError: this.safeString is not a function
I followed a solution offer by another SO post:
safeString: function(stringToCheck){
...
}
safeGithubPush(currentJob) {
...
if (
this.safeString(currentJob.payload.repoName) &&
this.safeString(currentJob.payload.repoOwner) &&
this.safeString(currentJob.payload.branchName)
) {
return true;
}
}
But this also gets a, TypeError: this.safeString is not a function.
I'm not using arrow functions, which is the explanation for this error on a different SO post
I don't think the reason is determinable with the code you are currently presenting. It likely has something to do with how you are calling safeGithubPush. If you do something that would change the this binding the this.safeString is going to fail.
const foo = {
fizz() {
console.log("fizz");
},
buzz() {
this.fizz();
}
};
// "this" is correct
foo.buzz();
// "this" has no fizz to call
const myFizz = foo.buzz;
myFizz();
Considering you are attaching these to module.exports I am going to guess that you pull these functions off in a require call and then try to use them bare which makes the problem obvious after looking at my example above:
// Ignore these 2 lines, they let this look like node
const module = {};
const require = () => module.exports;
// Ignore above 2 lines, they let this look like node
// Your module "some.js"
module.exports = {
safeString(str) {
return true;
},
safeGithubPush(currentJob) {
if (!this.safeString("some")) {
throw new Error("Not safe");
}
return true;
}
};
try {
// Some consumer module that doesn't work
const {safeGithubPush} = require("./some.js");
const isItSafe = safeGithubPush();
console.log(`Safe? ${isItSafe}`);
} catch (err) {
console.error("Didn't bind right \"this\"");
}
try {
// Some consumer module that DOES work
const someModule = require("./some.js");
const isItSafe = someModule.safeGithubPush();
console.log(`Safe? ${isItSafe}`);
} catch (err) {
console.error(err);
}
I would restructure this code. You say these are utility functions which makes me think you don't really want to have to structure them with this in mind.
Instead of attaching them all to module.exports at their definition, define them outside and directly reference the functions you want to use, then attach them to exports so other modules can use the functions:
function safeString(stringToCheck) {
return true;
}
function safeGithubPush(currentJob) {
if (!safeString("some")) {
throw new Error("Not safe");
}
return true;
}
module.exports = {
safeString,
safeGithubPush
};
I am using Firebase function to create an API and at the same time I Am using the Firebase Firestore as my database.
I am using Node.js to create the program.
I wanted to know how to create a function in Node.js.
I will be calling a code more than once and since I have been use to Java and Java has molecularity will it be possible in Node.js also?
This is my code
exports.new_user = functions.https.onRequest((req, res) => {
var abc=``;
if(a=='true')
{
abc=Function_A();//Get the results of Function A
}
else
{
abc=Function_B();//Get the results of Function B
//Then Call Function A
}
});
As shown in the code I would be calling the same function two times from different location depending upon the situation and then utilizing the result of it.
Is it possible to declare a function and then call if from different locations and then utilize its result?
Any help would be really appreciated as I am new to Node.js
If you are trying to just get a value back from the function it depends if you are doing synchronous (adding 2 numbers together) or asynchronous (doing an HTTP call)
synchronous:
let abc = 0;
if(a=='true')
{
abc = Function_A();//Get the results of Function A
}
else
{
abc = Function_B();//Get the results of Function B
//Then Call Function A
}
function Function_B() {
return 2+2;
}
function Function_A() {
return 1+1;
}
asynchronous:
let abc = 0;
if(a=='true')
{
Function_A(function(result) {
abc = result;
});//Get the results of Function A
}
else
{
Function_A(function(result) {
abc = result;
});//Get the results of Function A
}
function Function_B(callback) {
callback(2+2);
}
function Function_A(callback) {
callback(1+1);
}
Asynchronous with variable:
let abc = 0;
Function_A(2, function(result) {
abc = result; //should by 4
});//Get the results of Function A
function Function_A(myVar, callback) {
callback(myVar * 2);
}
I have this code in node js / firebase :
ref.child("recipts").once("value", function(usersSnap) {
usersSnap.forEach(function(reciptsSnap) {
reciptsSnap.forEach(function(reciptSnap) {
reciptSnap.ref.child("last_recipt").once("value", function(b) {
b.forEach(function(c) { //Here I fill some "product" object
});
});
reciptSnap.forEach(function(b) { //Here I fill some "product" object
});
});
});
});
I need to execute a function just when "reciptSnap" forEachs finished. How can I accomplish this, I try using a variable i++ and i-- but only work for one forEach iteration.
The function I call is for manipulating the product object I created with the filled data from the forEachs loops.
If I have understood correctly, you want to call a function when reciptsSnap.forEach is complete and all async tasks inside it are also complete.
For achieving this, you can use the index parameter and the original array that is passed to the callback function of forEach. (See Documentation)
The code will be like this:
(Note: The following code is without changing the current forEach loop structure used. However, re-writing the code with Promise or async would be a better & cleaner way to do it).
var loop1Done = false;
var loop2Done = false;
ref.child("recipts").once("value", function (usersSnap) {
usersSnap.forEach(function (reciptsSnap) {
reciptsSnap.forEach(function (reciptSnap, index, colA) {
const idx = index;
const col = colA;
reciptSnap.ref.child("last_recipt").once("value", function (b) {
const i = idx;
const c = col;
b.forEach(function (c, j, colB) { //Here I fill some "product" object
// Do what you want here
// Check if all done for this loop
if ((j >= colB.length) && (i >= c.length)) {
loop1Done = true;
// Check if all loops done
if (loop1Done && loop2Done) {
// Call final callback function
// e.g. myFinalCallback();
}
}
});
});
reciptSnap.forEach(function (b, k, colC) { //Here I fill some "product" object
const i = idx;
const c = col;
// Do what you want here
// Check if all done for this loop
if ((k >= colC.length) && (i >= c.length)) {
loop2Done = true;
// Check if all loops done
if (loop1Done && loop2Done) {
// Call final callback function
// e.g. myFinalCallback();
}
}
});
});
});
});
Try:
reciptSnap.child("last_recipt").forEach(function(b) {
b.forEach(function(c) {
//Here I fill some "product" object
});
});
This should work since all of your data should already have been fetched when you did "value" on the receipts node.
If this works, your code is no longer asynchronous and right after the last forEach, you can execute the function you wanted to.
reciptSnap.forEach(function(b) {
//Here I fill some "product" object
});
//Execute your function here
});
This is a bit foreign to me and I'm probably not understanding it correctly. This is what I have:
var imgModule = (function() {
var imgLocations = {};
var images = [];
imgLocations.setImage = function(img, location) {
imgLocations[img] = location;
}
imgLocations.getImg = function(img) {
return imgLocations[img];
}
imgLocations.setImageArray = function(img) {
images.push(img);
}
imgLocations.getImageArray = function() {
return images;
}
return imgLocations;
}());
I want to be able to access the imgLocations Object and images array from outside this function. The setting functions work, but
document.getElementById("but").onclick = function() {
console.log(imgModule.imgLocations.getImageArray());
console.log(imgModule.imgLocations.getImg(imgName));
}
Both return "undefined". How do I access these variables? And how can I improve this function? Please be patient with me and explain what I'm doing wrong :) I'm trying to learn it the right way instead of defining a global variable outside all functions.
The reason why this isn't working, is because your imgModule is returning the imgLocations object. That being the case, imgModule will actually be the imgLocations object. So you would access your methods like so:
imgModule.setImage()
imgModule.getImg()
imgModule.getImageArray()
imgModule.setImageArray()
And as #gillesc stated. If you are wanting to keep the current syntax of imgModule.imgLocations.getImg() then you could return the imgLocations like so
return {
imgLocations: imgLocations
}
doing so would allow you to add more functionality to your module
return {
imgLocations: imgLocations,
otherObject: otherObject
}
...
imgModule.otherObject.someFunctionCall();
The problem is you are returning the object created and are not setting it as a property of an object.
So in your case this is how it would work.
document.getElementById("but").onclick = function() {
console.log(imgModule.getImageArray());
console.log(imgModule.getImg(imgName));
}
What you need to do is return it like this
return {
imgLocations: imgLocations
}
If you want the API you are attending to create and still have access to the array which you can not do currently.
You don't access imgModule.imgLocations, since what you return is imgLocations, you should access them as:
document.getElementById("but").onclick = function() {
console.log(imgModule.getImageArray());
console.log(imgModule.getImg(imgName));
}
It seems you try to write module pattern.
For deep understanding, I recommend you following article:
The Module Pattern, by Addy Osmani
and pay attention to example with counter:
var testModule = (function () {
var counter = 0;
return {
incrementCounter: function () {
return counter++;
},
resetCounter: function () {
console.log( "counter value prior to reset: " + counter );
counter = 0;
}
};
})();
// Usage:
// Increment our counter
testModule.incrementCounter();
// Check the counter value and reset
// Outputs: counter value prior to reset: 1
testModule.resetCounter();