Develop Reference

Object element returning undefined with addEventListener

I am making a simple form which requests the user to input their project name and their name, along with some other info.
But each type of project has a different page, so to avoid copying and pasting the same getElementById and addEventListener functions in each page, I've made a module with those functions so every page handles it as needed. This is one of the pages:
// (imports)...
let project = {
author: null,
name: null,
mission: {
file: null,
path: null,
},
sd: {
code: null,
path: null,
},
modloaderfolder: null,
};
window.addEventListener("DOMContentLoaded", () => {
project.mission = handleMission();
project.sd = handleSD();
project.modloaderfolder = handleModloader();
project.name = handleName();
project.author = handleAuthor();
// ...
The problem is that the objects' elements are returning undefined in the two following functions:
export function handleName() {
const project = {};
const txt_name = document.getElementById("name");
txt_name.addEventListener("change", () => {
project.name = txt_name.value;
});
return project.name;
}
export function handleAuthor() {
const project = {};
const txt_author = document.getElementById("author");
txt_author.addEventListener("change", () => {
project.author = txt_author.value;
});
return project.author;
}
// Returns undefined
Whats intriguing for me is that some other functions are working as intended, I can't find out why. These are the corretly working functions:
export function handleSD() {
const project = { sd: {} };
const input_sd = document.getElementById("sd");
input_sd.addEventListener("change", () => {
document.getElementById("sel-sd").innerHTML = "";
Array.from(input_sd.files).forEach((file) => {
document
.getElementById("sel-sd")
.insertAdjacentHTML("beforeend", `<option>${file.name}</option>`);
});
if (!input_sd.files[0]) return;
const path = input_sd.files[0].path;
project.sd.path = path.substring(0, path.lastIndexOf("\\")) + "\\";
project.sd.code = project.sd.path.substring(
project.sd.path.lastIndexOf("\\") - 5,
project.sd.path.length - 1
);
});
return project.sd;
}
// This function correctly returns "sd: { path: ..., code: ...}"
What I noticed is that by returning an object, it returns and updates correctly for each change, but while returning an object's element, it aways returns undefined.

which is empty and nothing will change it because copying a primitive value is by value but the object that holds the key of the string, and as soon as the onchange function is activated it changes the value of your key in the object and it automatically changes in your object too because it is copied by Reference.
You can read more about this topic here

Pagination in TypeORM/NestJS

I have to introduce pagination in findAll() method. I really dont know how to do it. I tried but it is giving so many errors. I used findAndCount() method given by typeorm for that, But I am not sure how it will work.
As of now below method returning all the record. I need to return at a time 10 records. Please suggest what modification I need to do.
async findAll(queryCertificateDto: QueryCertificateDto,page=1): Promise<PaginatedResult> {
let { country, sponser } = queryCertificateDto;
const query = this.certificateRepository.createQueryBuilder('certificate');
if (sponser) {
sponser = sponser.toUpperCase();
query.andWhere('Upper(certificate.sponser)=:sponser', { sponser });
}
if (country) {
country = country.toUpperCase();
query.andWhere('Upper(certificate.country)=:country', { country });
}
const certificates = query.getMany();
return certificates;
}
this is PaginatedResult file.
export class PaginatedResult {
data: any[];
meta: {
total: number;
page: number;
last_page: number;
};
}
I tried changing code of findAll() but where clause is giving error. I am not sure how to handle query.getMany() in pagination.
const take = query.take || 10
const skip = query.skip || 0
const [result, total] = await this.certificateRepository.findAndCount(
{
where: query.getMany(), //this is giving error
take:take,
skip:skip
}
);
return result;
I need to introduce pagination in this method. Any help will be really helpful.

Typeorm has a really nice method specific to your usecase findAndCount
async findAll(queryCertificateDto: QueryCertificateDto): Promise<PaginatedResult> {
const take = queryCertificateDto.take || 10
const skip = queryCertificateDto.skip || 0
const country = queryCertificateDto.keyword || ''
const sponser = queryCertificateDto.sponser || ''
const query = this.certificateRepository.createQueryBuilder('certificate');
const [result, total] = await this.certificateRepository.findAndCount(
{
where: { country: Like('%' + country + '%') AND sponser: Like('%' + sponser + '%') }, order: { name: "DESC" },
take: take,
skip: skip
}
);
return {
data: result,
count: total
};
}
More documentation about Repository class can be found here

You don't need the .getMany() with your where in the last code, the result is an array of the data you need.
From your first code, you can do this:
async findAll(queryCertificateDto: QueryCertificateDto,page=1): Promise<PaginatedResult> {
// let's say limit and offset are passed here too
let { country, sponser, limit, offset } = queryCertificateDto;
const query = this.certificateRepository.createQueryBuilder('certificate');
if (sponser) {
sponser = sponser.toUpperCase();
query.andWhere('certificate.sponser = :sponser', { sponser });
}
if (country) {
country = country.toUpperCase();
query.andWhere('certificate.country = :country', { country });
}
// limit and take mean the same thing, while skip and offset mean the same thing
const certificates = await query
.orderBy("certificate.id", "ASC")
.limit(limit || 10)
.offset(offset || 0)
.getMany();
// if you want to count just replace the `.getMany()` with `.getManyandCount()`;
return certificates;
}```

What is the best way for reducing multiple if statement?

I have a helper function that builds object with appropriate query properties. I use this object as a body in my promise request. What is the most elegant way for refactoring multiple if statements? Here is a function:
getQueryParams = (query, pagination, sorting) => {
let queryParam = {}
if (pagination && pagination.pageNumber) {
queryParam.page = `${pagination.pageNumber}`
}
if (pagination && pagination.rowsOnPage) {
queryParam.size = `${pagination.rowsOnPage}`
}
if (query) {
const updatedQuery = encodeURIComponent(query)
queryParam.q = `${updatedQuery}`
}
if (sorting) {
queryParam.sort = `${sorting.isDescending ? '-' : ''}${sorting.name}`
}
return service.get(`/my-url/`, queryParam).then(result => {
return result
})
}

If service checks its parameters (as it should), you could benefit from the default parameters. Something like this:
const getQueryParams = (
query = '',
pagination = {pageNumber: 0, rowsOnPage: 0},
sorting = {isDescending: '', name: ''}
) => {
const queryParam = {
page: pagination.pageNumber,
size: pagination.rowsOnPage,
q: encodeURIComponent(query),
sort: `${sorting.isDescending}${sorting.name}`
}
return ...;
};
A live example to play with at jsfiddle.

This is an idea how it could looks like, but you need to adopt your params before:
const query = new URLSearchParams();
Object.keys(params).forEach(key => {
if (params[key]) {
query.append(key, params[key]);
}
});

Object properties are undefined, the object itself shows all the data though

I'm building an Single Page application for a minor project. I've been trying to save data from API call's to the Movie Database in an object. If i console.log the object, I can see all its properties and values. If I console.log the object.property, it returns 'undefined'. This is the code:
(() => {
"use strict"
/* Saving sections to variables
--------------------------------------------------------------*/
const movieList = document.getElementsByClassName('movie_list')[0];
const movieSingle = document.getElementsByClassName('movie_single')[0];
/* All standard filters for displaying movies
--------------------------------------------------------------*/
const allFilters = {
trending: 'movie/popular',
toplist: 'movie/top_rated',
latest: 'movie/now_playing',
upcoming: 'movie/upcoming'
};
const allData = {};
/* Initialize app - Get al standard data and save it in object
--------------------------------------------------------------*/
const app = {
init() {
getData(allFilters.trending, 'popular');
getData(allFilters.toplist, 'toplist');
getData(allFilters.latest, 'latest');
getData(allFilters.upcoming, 'upcoming');
this.startPage();
},
startPage() {
window.location.hash = "trending";
}
}
/* Function for getting data from the API
--------------------------------------------------------------*/
const getData = (filter, key) => {
const request = new XMLHttpRequest();
const apiKey = '?api_key=xxx';
const getUrl = `https://api.themoviedb.org/3/${filter}${apiKey}`;
request.open('GET', getUrl, true);
request.onload = () => {
if (request.status >= 200 && request.status < 400) {
let data = JSON.parse(request.responseText);
data.filter = key;
cleanData.init(data);
} else {
window.location.hash = 'random';
}
};
request.onerror = () => {
console.error('Error');
};
request.send();
};
/* Check if the data is list or single, and clean up
--------------------------------------------------------------*/
const cleanData = {
init(originalData) {
if (!originalData.results) {
this.single(originalData);
} else {
allData[originalData.filter] = originalData;
}
},
list(data) {
data.results.map(function(el) {
el.backdrop_path = `https://image.tmdb.org/t/p/w500/${el.backdrop_path}`;
});
let attributes = {
movie_image: {
src: function() {
return this.backdrop_path;
},
alt: function() {
return this.title;
}
},
title_url: {
href: function() {
return `#movie/${this.id}/${this.title}`;
}
}
}
showList(data.results, attributes);
},
single(data) {
data.poster_path = `https://image.tmdb.org/t/p/w500/${data.poster_path}`;
data.budget = formatCurrency(data.budget);
data.revenue = formatCurrency(data.revenue);
data.runtime = `${(data.runtime / 60).toFixed(1)} uur`;
data.imdb_id = `http://www.imdb.com/title/${data.imdb_id}`;
let attributes = {
movie_image: {
src: function() {
return this.poster_path;
},
alt: function() {
return this.title;
}
},
imdb_url: {
href: function() {
return this.imdb_id
}
},
similar_url: {
href: function() {
return `#movie/${this.id}/${this.title}/similar`
}
}
};
showSingle(data, attributes);
}
};
const showList = (cleanedData, attributes) => {
movieList.classList.remove('hidden');
movieSingle.classList.add('hidden');
Transparency.render(movieList, cleanedData, attributes);
};
const showSingle = (cleanedData, attributes) => {
movieSingle.classList.remove('hidden');
movieList.classList.add('hidden');
Transparency.render(movieSingle, cleanedData, attributes);
}
const formatCurrency = amount => {
amount = amount.toFixed(0).replace(/./g, function(c, i, a) {
return i && c !== "." && ((a.length - i) % 3 === 0) ? '.' + c : c;
});
return `€${amount},-`;
};
app.init();
console.log(allData); // Returns object with 4 properties: trending, toplist, latest & upcoming. Each property is filled with 20 results (movies with data) from the API.
console.log(allData.trending) // Returns 'undefined' (each property I've tried).
console.log(allData['trending']) // Returns 'undefined'
Object.keys(allData); // Returns an empty Array []
})();
When I use console.log(allData) I see 4 properties, all filled with the results from the API. But when i do console.log(allData.trending) or console.log(allData['trending']) it returns 'Undefined' in the console. Has anyone an idea how to fix this?

When you call app.init() it fires the init and sends the api call(s) to fetch data.
The call to fetch data is Asynchronous, which means it doesn't wait for the response to continue execution. So it goes ahead and executes next lines of code, which are your console.logs. At this time the API calls haven't responded with the data, so when you try to access data.property it fails as the data is not yet here.
When you do log(data) it creates a log of the reference to data, which gets updated in the log when the reference is filled with a value later. To get the value of data at that instance and prevent updating later you can try log(JSON.stringify(data)). When you do that you get a consistent result, none of your logs work, which is the actual behaviour.
To get your logs work, look into the success/load callback of you A(synchronous)JAX request, log it from there. Or if you constructed allData later in cleanData then call the logs after cleanData function.
So to answer your question, none of your logs should work as it is an asynchronous call. You are getting the allData logged due to the way console.log works with references that are updated later, use console.log(JSON.stringify(allData)) to get the actual snapshot of Object

Reducer cannot read property 'photos' of undefined? What am I doing wrong?

Here is the initial state of my reducer, and I need to set it up in this way due to some post processing I need to do:
const initialState = {
showAll: {
photos: null
}
}
Basically, I have a page where you see all your photos, and you can tag certain ones as your pinned photos.
Here's part of my reducer logic:
if (state.showAll.photos) {
const showAllState = state.showAll.photos;
showAllState.map(m => {
if (action.payload.id === m.id) {
m.pinned = true;
}
});
showAllAfterPin = showAllState;
} else {
showAllAfterPin = state.showAll.photos;
}
However, I get an error saying cannot read property 'photos' of undefined and I'm not sure what I am doing wrong.

Might be easier to just set your photos in initialState to empty array [] instead of null.
Another thing, your reducer should not mutate your state object.
Doing const showAllState = state.showAll.photos doesn't make it a new object.
Last thing, showAllState.map(...) needs to return an item inside the function body. It will create a new array.
Here's something you can do...
const { photos = [] } = state.showAll;
const updatedPhotos = photos.map(photo => {
if (action.payload.id === photo.id) {
return Object.assign({}, photo, { pinned: true })
}
return photo;
});
// return entire state if this is inside your root reducer
return {
...state,
showAll {
...state.showAll,
photos: updatedPhotos
}
}