How can I overwrite a module export value?
Currently I have this:
temp.js
let lastrsss = '';
module.exports = {
lastrsss
};
I try overwrite the value with this:
const temprss = require('../../temp');
temprss.lastrsss = "https://something.com";
It works, but same time it doesn't. I think it saves in memory or I don't know. It doesn't save in temp.js. How can I do that it will save in temp.js?
There are a couple ways to handle this. A nice clean one is to define a getter and setter:
temp.js
lastrsss = "hello"
module.exports = {
get lastrsss() {
return lastrsss
},
set lastrsss(val){
lastrsss = val
}
}
Now you can use them just like regular properties:
let tempres = require('./test2.js')
console.log(tempres.lastrsss) // hello
tempres.lastrsss = "goodbye"
console.log(tempres.lastrsss) // goodbye
Export a function to create and set a value in the lastrsss.
Try something like this:
function setLastrsss(value) {
let lastrsss = value;
return lastrsss;
}
module.exports = {
setLastrsss;
}
Related
I need to convert a Symbol to string in order to create a unique key in Redis, but I can't.
I've already tried to use Object.toString(obj) and String(obj) but I get errors or [Object] results¡.
This is the controller
const name = req.params.name;
let obj;
obj.data.name = {
[Op.like]: '%' + name + '%'
};
}
This is redis controller where I use stringify. I use obj as a parameter.
const hashed = crypto.createHmac('sha256', secretHashKey)
.update(JSON.stringify(obj))
.digest('hex');
I expect an output based on my parameter 'obj' but now it's not getting it so I can't create unique keys for different values.
Maybe a little bit too late, but I hope that somebody else find this useful.
I was looking for something exactly as you: use with Sequelize in a Redis cache.
Mine is TypeScript, convert to JavaScript just by removing the typings.
export function JsonStringifyWithSymbols(object: any, clean?: boolean): string {
return JSON.stringify(object, (_, value) => {
if (typeof value === 'object' && !Array.isArray(value) && value !== null) {
const props = [...Object.getOwnPropertyNames(value), ...Object.getOwnPropertySymbols(value)];
const replacement: Record<string, any> = {};
for (const k of props) {
if (typeof k === 'symbol') {
replacement[`Symbol:${Symbol.keyFor(k)}`] = value[k];
} else {
replacement[k] = value[k];
}
}
return replacement;
}
return value;
});
}
If you're meaning these Symbols you can't convert them to a string.
They're created to be unique and "unreversable", so you can use them also for keep more "secure" various properties or methods. Example:
const a = Symbol('a')
class Foobar {
constructor (_a) {
this[a] = _a
}
}
const foobar = new Foobar('aaa')
console.log(foobar) // output: Foobar { [Symbol(a)]: 'aaa' }
const fake = Symbol('a')
foobar[fake] = 'fake'
console.log(foobar) // output: Foobar { [Symbol(a)]: 'aaa', [Symbol(a)]: 'fake' }
You can't corrupt the original one, unless you have the original Symbol.
Another example (info about the JSON.stringify here):
const a = Symbol('a')
const foobar = {}
foobar[a] = 'aaa'
console.log(foobar) // output: { [Symbol(a)]: 'aaa' }
console.log(JSON.stringify(foobar)) // output: {}
const fake = Symbol('a')
foobar[fake] = 'fake'
console.log(foobar) // output: { [Symbol(a)]: 'aaa', [Symbol(a)]: 'fake' }
Hope these info will help you.
I have a multidimensional object and using Vue, I am trying to make the inner object reactive.
My object looks like this:
data() {
return {
myObject: {}
}
}
And the filled data looks like this:
myObject: {
1: { // (client)
0: "X", // (index) : (value)
1: "Y"
},
2: {
0: "A",
2: "B"
}
}
If I try using:
let value = "X";
let client = 1;
let index = 1;
let obj = {};
obj[client][index] = value;
this.myObject = Object.assign({}, this.myObject, obj);
It throws an error:
TypeError: Cannot set property '0' of undefined
And if I try below, it overwrites the initial values as it is initially setting the object to {}
let obj = {};
obj[index] = value;
let parentObj = {};
parentObj[client] = obj;
this.myObject = Object.assign({}, this.myObject, parentObj);
What is the proper way of adding the values to the multidimensional object?
In javascript, dim2Thing[1][1] = ... expressions require dim2Thing[1] to exist. This is why you get the error you mentioned. So you can do two expressions, which should work fine:
dim2Thing[1] = dim2Thing[1] || {}
dim2Thing[1][1] = otherThing
For the last block, you mention that it "overwrites the initial values"
I think what's actually happening here is just that Object.assign is not recursive. It only merges top-level keys. So if parentObj has a key that over-laps with this.myObj, then sub-keys will be lost.
Object.assign({ a: { b: 2} }, { a: { c: 3 } }) // returns { a: { c: 3 } }
This is what I interpret your code as trying to do - though I am unfamiliar with vue.js at this time, so I cannot assure it will have the desired result to your webpage:
let value = "X";
let client = 1;
let index = 1;
const newObj = Object.assign({}, this.myObject);
// if you have lodash _.set is handy
newObj[client] = newObj[client] || {}; // whatever was there, or a new object
newObj[client][index] = value
this.myObject = newObj
Just use an array, thats reactive by design.
If you need to get elements from the array in your template or anywhere just add a find method
// temp
late
<div v-for="(value, idx) in myArray">{{find(obj => obj.id === idx)}}</div>
methods: {
find (searchFunction) {
return this.myArray.find(searchFunction)
}
}
I have the following code structure :
const finalCall = require('./final.js');
function Func(){
this.process = {
initCall: function(params, callback){
let proParams;
//processing...
return finalCall(proParams, callback);
}
}
}
Now I need to test if my initCall function correctly processes the params and makes call to finalCall. I need to know how do I create a spy on my finalCall function, so when it gets called, I can track the proParams.
I have tried something like :
const func = new Func();
let proParams = null;
spyOn(func.process.initCall, "finalCall").and.callFake(function(pParams, callback){
proParams = pParams;
});
let params = { };
func.process.initCall(params, null);
expect(func.process.initCall.finalCall).toHaveBeenCalled();
expect(proParams).toEqual('...');
I am missing on what object I can access finalCall, or if there is another way to do so. Thanks in advance.
Finally I found a workaround to my problem. I created a prototype of the function finalCall() in my constructor Const, and put a spyOn on its object.
Solution
Main module:
const finalCall = require('./final.js');
function Func(){
const self = this;
this.process = {
initCall: function(params, callback){
let proParams;
//processing...
return self.finalCall(proParams, callback);
}
}
}
Func.prototype = finalCall;
and in my Spec file:
const func = new Func();
let proParams = null;
spyOn(const, finalCall);
let params = { };
func.process.initCall(params, null);
expect(func.finalCall).toHaveBeenCalled();
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();
I want to write a JS library and handle it like this:
var c1 = Module.Class();
c1.init();
var c1 = Module.Class();
c2.init();
And of course, c1 and c2 can not share the same variables.
I think I know how to do this with objects, it would be:
var Module = {
Class = {
init = function(){
...
}
}
}
But the problem is I can't have multiple instances of Class if I write in this way.
So I'm trying to achieve the same with function, but I don't think I'm doing it right.
(function() {
var Module;
window.Module = Module = {};
function Class( i ) {
//How can "this" refer to Class instead of Module?
this.initial = i;
}
Class.prototype.execute = function() {
...
}
//Public
Module.Class = Class;
})();
I don't have a clue if it's even possible, but I accept suggestions of other way to create this module.
I don't know if it's relevant also, but I'm using jQuery inside this library.
Usage:
var c1 = Module.Class("c");
var c2 = Module.Class("a");
var n = c1.initial(); // equals 'c'
c1.initial("s");
n = c1.initial(); // equals 's'
Module Code:
(function(window) {
var Module = window.Module = {};
var Class = Module.Class = function(initial)
{
return new Module.Class.fn.init(initial);
};
Class.fn = Class.prototype = {
init: function(initial) {
this._initial = initial;
},
initial: function(v){
if (v !== undefined) {
this._initial = v;
return this;
}
return this._initial;
}
};
Class.fn.init.prototype = Class.fn;
})(window || this);
This is using the JavaScript "Module" Design Pattern; which is the same design pattern used by JavaScript libraries such as jQuery.
Here's a nice tutorial on the "Module" pattern:
JavaScript Module Pattern: In-Depth