Engineering diary
Solution: (Typescript)
(range as Date[]).sort((a, b) => a.valueOf() - b.valueOf());My first thought was why not just:
(range as Date[]).sort()But that does not work. Have a look at the MDN documents and you will see the comparison is done with character’s Unicode code.
Try this in your browsers console to see the solution working
const range = [
new Date("2020-09-10"),
new Date("2020-12-20"),
new Date("2020-11-12"),
];
range.sort((a, b) => a.valueOf() - b.valueOf())I always disliked dates in JS, but as time goes by confidence grows. It does not help that I avoid reaching for external packages unless it is really necessary.
Today I needed to generate arrays of numbers that represent days between two dates.
// Outcome needed. Inputs 2020-10-28 and 2020-11-06
const labels = [28,29,30,13,1,2,3,4,5,6];
// Solution
export const getDatesBetweenDates = (
startDate: string,
endDate: string
): number[] => {
const dates: number[] = [];
const start = new Date(startDate);
const end = new Date(endDate);
while (start <= end) {
dates.push(start.getDate());
start.setDate(start.getDate() + 1);
}
return dates;
};I have no idea why I thought that would be hard
There are many ways to do this by looping over the array, then using something like .some() or .findIndex().
How about this as an elegant and simple solution?
[...new Map(users.map((item) => [item.id, item])).values()]The use case is a collection of aggregated data that could have multiple copies of a user. I needed to remove duplicates:
const users = [
{id: "1234", name: "kirk"},
{id: "6789", name: "spock"},
{id: "1234", name: "kirk"},
{id: "1234", name: "kirk"},
{id: "rtyu", name: "bones"},
]
console.log([...new Map(users.map((item) => [item.id, item])).values()])Copy and paste the code below into your browser console pane to see it work
const users = [
{id: "1234", name: "kirk"},
{id: "6789", name: "spock"},
{id: "1234", name: "kirk"},
{id: "1234", name: "kirk"},
{id: "rtyu", name: "bones"},
]
[...new Map(users.map((item) => [item.id, item])).values()]I have been using Node.js with Express.js for just over a year now and Typescript for 8 months building and maintaining micro services for an SME business operating globally.
The project is at: https://github.com/daveKoala/typescript-api-starter.git
Of the 1/2 dozen I’ve created from scratch each has grown in sophistication. I now know what I want for each REST api service (in no real order):
I am nearly there…
Node.js, Express.js and Typescript. Not much to say about this that has not already been said.
Multiple Environments: This is a bit trickier as conventional wisdom is that env values are not stored within the repo. This makes perfect sense, however the projects I am working with have 3 people at most and keeping the env within the private repo lets us quickly create new services and keep all settings, pipelines etc together with minimal fuss. It was a decision we made as a group 18 months ago and has paid off. I know there will be eye rolling at this tho’.
Unit Testing: I using Mocha.js and Chai.js no real reason apart from it works for me. There are 2 specific requirements. The first being that test scripts sit alongside the code being tested and the second is the option to publish test results. This project does both.
External Cache: Middleware on routes that intercepts the request, hashes the url and body to make an ID then queries the cache. A null response passes the request to the controller and caches the results.
‘Developer mode’: Easy with Nodemon and scripts within the package.json file. There are a few other useful scripts including a “lazy script” that runs tests, linting, audits and a build process.
Debugging: I’ll leave that to Visual Studio Code and commit any settings files.
All end points versioned and documented: Using Swagger and OpenDoc to create nice api docs. Added advantage is that you can link/download to the OpenDocs JSON into Postman to create collections.
Versioning: I opted for the “version via the request header” approach. Why? I like that the urls don’t change and because it is strict. Strict as in, if you fail to request a version you get feedback telling you what you need to do. The main thing about versioning is declaring a contract and sticking to it.
Authentication and Authorisation: Separate middleware that can leverage different methods specified by the project.
Custom errors: Easy enough, create meaningful error messages and responses. They also accept plugins for external logging.
Re-try connections if they initially fail: Also known as a Circuit Breaker pattern.
Project auto saves and lints: Let Visual Studio handle this and commit settings to the project.
CI/CD Pipeline: Convention over configuration and making use of files like Azure Pipelines YAML files to describe and run CI/CD processes.
This is an ongoing project and can be found at: https://github.com/daveKoala/typescript-api-starter.git
I had a large list that a user could reorder by dragging and dropping. All work beautifully.
Except persisting the changes to the database. I did not want the an API call for every drop action or a button that the user clicked that said, “Save list”.
Solution:
Its a Vue.js project and the drag and drop had two events called “start” and “end”. These would call the corresponding methods below.
“endDrag” starts a timer that will run the supplied method in 1.5 seconds after the dragging has stopped. If the user starts “dragging” again the timer is cancelled
methods: {
endDrag(): void {
this.timer = setTimeout(this.distpatchOrderedList, 1500);
this.drag = false;
},
startDrag(): void {
clearTimeout(this.timer);
this.drag = true;
},
distpatchOrderedList(): void {
// Do some magic
}
}I’ve been using Typescript for 12 months and every now and then I get blocked. I used to do a fair bit of ‘typescript ignore’ in my code just to keep things moving and depend on my tests to throw up mistakes.
This I think ha caught me out a few times in different circumstances.
interface Options {
id: string;
name: string;
}
const options: Options = {id: "qwerty", name: "andy pandy"}
Object(options).forEach(key => {
localOptions[key] = options[key]
});The above would not compile and give the following message (note if I set the line to be ignored the code still worked)
Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index type ‘xxxx’. No index signature with a parameter of type ‘string’ was found on type ‘xxxx’
So how to comply with Typescript?
I found two options. One went about extending the object constructor and adding overloads the second is type-casting. Extending the object constructor is probably more “correct” but type-casting worked and when you read the code it simpler to understand (IMHO)
interface Options {
id: string;
name: string;
}
const options: Options = {id: "qwerty", name: "andy pandy"}
Object(options).forEach(key => {
localOptions[key as keyof Options] = options[key as keyof Options]
});Does it work and does it address the issue? Yes it does.
I need to check if a date string is within a date range.
// Set up
const dateRange = ["2020-07-30", "2020-07-20"];
let n = 0;
const collection = [
{ "createdOn": "2020-07-01", title: `title # ${ n++ }` },
{ "createdOn": "2020-07-10", title: `title # ${ n++ }` },
{ "createdOn": "2020-07-20", title: `title # ${ n++ }` }, // Include
{ "createdOn": "2020-07-21", title: `title # ${ n++ }` }, // Include
{ "createdOn": "2020-07-21", title: `title # ${ n++ }` }, // Include
{ "createdOn": "2020-07-30", title: `title # ${ n++ }` }, // Include
{ "createdOn": "2020-07-30", title: `title # ${ n++ }` }, // Include
{ "createdOn": "2020-07-31", title: `title # ${ n++ }` },
];
// Solution
const filter = (collection, dateRange) => {
const dates = [...dateRange].sort(); // Sorts the date range: from -> to
return collection.filter(item => item.createdOn >= dates[0] && item.createdOn <= dates[1]); // returns either array of objects or an empty array
}
console.table(filter(collection, dateRange));
┌─────────┬──────────────┬─────────────┐
│ (index) │ createdOn │ title │
├─────────┼──────────────┼─────────────┤
│ 0 │ '2020-07-20' │ 'title # 2' │
│ 1 │ '2020-07-21' │ 'title # 3' │
│ 2 │ '2020-07-21' │ 'title # 4' │
│ 3 │ '2020-07-30' │ 'title # 5' │
│ 4 │ '2020-07-30' │ 'title # 6' │
└─────────┴──────────────┴─────────────┘
Every time I have anything to do with manipulating dates in JavaScript I need to stop and refresh my memory. Yes, there are amazing packages from Moment.js and Date-fns.
But why should I import a library just to a few simple things?
Here are my notes on dates (it is not an exhaustive list).
There are 24 time zones mix in that many also have day light saving which adds/subtracts an hour. When a country does this is not constant around the world and is not fixed
So, in JavaScript there are two times:
Date methods in JavaScript return Local time
Here I need to create a date range array. The range covers 30 days
const autoDays = () => {
const daysInThePast = 30;
const today = new Date();
const pastDate = new Date(today);
pastDate.setDate(today.getDate() - daysInThePast);
return [
pastDate.toISOString().substring(0, 10),
today.toISOString().substring(0, 10)
];
}I had a requirement to automate the CI/CD pipeline of an existing Vue.js project.
What was asked…
The project repo was already in Azure Dev Ops
trigger:
- releases/dev
pool:
vmImage: "ubuntu-latest"
steps:
- task: NodeTool@0
inputs:
versionSpec: "12.x"
displayName: "Install Node.js"
- script: |
npm install
npm run test:unit
displayName: "npm install"
- script: |
npm run test:unit
displayName: "npm run test:unit"
- script: |
npm run build:dev
displayName: "npm run build:dev"
- task: AzureCLI@2
displayName: "Copy files to blob storage"
inputs:
azureSubscription: 'Faux-Development-ltd'
scriptType: 'bash'
scriptLocation: 'inlineScript'
inlineScript: 'az storage blob upload-batch -d \$web --account- name "blobStoreName" -s "dist" --connection-string "DefaultEndpointsProtocol=https;AccountName=xxxxxx;AccountKey=123456789123456789/qwerty/qwertybangbang==;EndpointSuffix=core.windows.net"'
The only sticking points where.
The blob store container is called $web which look like a variable in the shell script so I had to use \$web
I have the following and need to test if a user id is present anywhere in the collection.
const meetingCollection = [
{ id: "2", userIds: [12, 34, 55, 6, 7, 43543, 45345, 545] },
{ id: "21", userIds: [3, 425, 5, 33, 7, 68, 76, 99, 66, 99] },
{ id: "22", userIds: [767, 5654756, 5658, 86, 45, 23456, 666] },
{ id: "23", userIds: [6, 43562, 5645747, 4654, 2577, 4345, 45777] },
{ id: "24", userIds: [45645, 124, 4, 435, 6, 7755, 7, 8] },
{ id: "25", userIds: [1, 2, 455, 647, 753] },
]const queryString = 7755;
meetingCollection.some(m => m.userIds.some(userId => userId === queryString))
Array.prototype.some() tests the method against each “row” of the collection and returns true on the first hit and then stops. If you have a 1000 elements and the method returns true on the 10th iteration .some() stops looping over the collection and returns true.
If a method fails to return true then false is returned.
The above example I’ve nested .some()
Try this in the console….
const meetingCollection = [
{ id: "2", userIds: [12, 34, 55, 6, 7, 43543, 45345, 545] },
{ id: "21", userIds: [3, 425, 5, 33, 7, 68, 76, 99, 66, 99] },
{ id: "22", userIds: [767, 5654756, 5658, 86, 45, 23456, 666] },
{ id: "23", userIds: [6, 43562, 5645747, 4654, 2577, 4345, 45777] },
{ id: "24", userIds: [45645, 124, 4, 435, 6, 7755, 7, 8] },
{ id: "25", userIds: [1, 2, 455, 647, 753] },
]
const findId = (queryString) => {
return meetingCollection.some(m => m.userIds.some(userId => userId === queryString))
}
console.log(findId(2577)); // true
console.log(findId(257)); // false