I have a function in a module that simulates shell.
function shell() {
while(1) {
let code = readline.question(">> ");
if(code == "") continue;
if(code == "exit") break;
try {
console.log(eval(code));
} catch (e) {
console.log(e.message);
}
}
}
module.exports = shell;
I'm calling this shell function inside another js file in hope of accessing all the variables and functions defined inside that caller function. Like below:
const shell = require('./shell.js');
var EXPIRY_DATES = ["28MAY2020"];
shell();
function parse_data() {
return "somedata";
}
But I'm not able to access EXPIRY_DATES and parse_data() from inside the shell. How to do this?
(I tried call and bind but not successful.)
Consider passing an object containing the properties (variables) you want the other script to be able to access, then reference that object when evaling:
function shell(vars) {
const result = eval('vars.EXPIRY_DATES');
console.log(result);
// other code in shell
}
(() => {
var EXPIRY_DATES = ["28MAY2020"];
shell({ EXPIRY_DATES });
module.exports = shell;
})();
Logged result:
[ '28MAY2020' ]
Related
I install a library/module but I am curious how they do it
const modules = require('abc');
const app = new modules('123');
const client = app.f1('abcdef').f2('ghi');
console.log(client.to());
const client2 = app.f1('1111111').f2('2222');
console.log(client2.to());
console.log(client.to());
result is 123:abcdef-ghi
result is 123:1111111-2222
result is 123:abcdef-ghi
how they did it?
i want to create that example lib/module
please give me sample code
Depending on your exact requirements, something like this seems to work:
let state = Symbol("private")
class App {
constructor(arg) {
this[state] = arg
}
f1 = arg => new App(this[state] + ":" + arg)
f2 = arg => new App(this[state] + "-" + arg)
to = () => this[state]
}
Here each of the chainable method returns a new instance of the class, each keeping the temporary result as a local state. The to() method returns that state.
This is what I use for doing function().anotherFunction()
function func() {
console.log("ran func")
return {
"anotherFunc": function () {
console.log("ran another func")
}
}
}
func().anotherFunc()
You can also just return a object
const returnData = {
"anotherFunc": function () {
console.log("ran another func")
}
}
function func() {
console.log("ran func")
return returnData
}
func().anotherFunc()
Example of use:
function word1(in_1) {
return {
"word2": function (in_2) {
console.log(`Inputs: ${in_1} ${in_2}`)
}
}
}
word1("Hello").word2("World")
// Expected output: Inputs: Hello World
I have NodeJS program.
In one class, I have various utility methods. One function, safeGithubPush, calls safeString, another func in the same class
module.exports = {
safeString(stringToCheck) {
console.log(validator.isAscii(stringToCheck), validator.matches(stringToCheck, /^((\w)*[-.]?(\w)*)*$/))
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 have a function that I need to pass to a class I have defined in nodeJs.
The use case scenario is I want to give the implementer of the class the control of what to do with the data received from createCall function. I don't mind if the method becomes a member function of the class. Any help would be appreciated.
//Function to pass. Defined by the person using the class in their project.
var someFunction = function(data){
console.log(data)
}
//And I have a class i.e. the library.
class A {
constructor(user, handler) {
this.user = user;
this.notificationHandler = handler;
}
createCall(){
var result = new Promise (function(resolve,reject) {
resolve(callApi());
});
//doesn't work. Keeps saying notificationHandler is not a function
result.then(function(resp) {
this.notificationHandler(resp);
}) ;
//I want to pass this resp back to the function I had passed in the
// constructor.
//How do I achieve this.
}
callApi(){ ...somecode... }
}
// The user creates an object of the class like this
var obj = new A("abc#gmail.com", someFunction);
obj.createCall(); // This call should execute the logic inside someFunction after the resp is received.
Arrow functions (if your Node version supports them) are convenient here:
class A {
constructor(user, handler) {
this.user = user;
this.notificationHandler = handler;
}
createCall() {
var result = new Promise(resolve => {
// we're fine here, `this` is the current A instance
resolve(this.callApi());
});
result.then(resp => {
this.notificationHandler(resp);
});
}
callApi() {
// Some code here...
}
}
Inside arrow functions, this refers to the context that defined such functions, in our case the current instance of A. The old school way (ECMA 5) would be:
createCall() {
// save current instance in a variable for further use
// inside callback functions
var self = this;
var result = new Promise(function(resolve) {
// here `this` is completely irrelevant;
// we need to use `self`
resolve(self.callApi());
});
result.then(function(resp) {
self.notificationHandler(resp);
});
}
Check here for details: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions#No_separate_this
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();