JavaScript and TypeScript developers often find themselves writing the same conditions repeatedly. If you're a web developer, you've probably encountered code like this:
const handleSaveTextKeydown = (event: KeyboardEvent) => { if (event.key === 'Enter') { //... save text } }
In this case, event.key is of type string, and it's easy to introduce bugs by accidentally including a space in 'Enter ', for example.
Why not encapsulate this condition in a function?
const handleSaveTextKeydown = (event: KeyboardEvent) => { if (checkIsEnterKey(event.key)) { //... save text } }
This ensures that all checks for the Enter key are consistent and reliable.
Now, consider this validation:
type Value = null | object; const value = {} as Value; if (typeof value === 'object') { value; // value type is null | object }
Even though TypeScript is smart, value inside the condition remains of type Value. This is because typeof null returns 'object'.
So, you need to write:
if (value !== null && typeof value === 'object') { value; // value type is object }
Many developers might not encapsulate this into a function and instead write it repeatedly whenever they encounter this situation.
How many times have you written the same condition in your life?
How many times have you made the same mistake?
How many more times will you write the same condition in the future?
If it were me, I would do this:
if (checkIsObject(value)) { value; // value type is object }
There are many benefits to encapsulating generic conditions in functions.
Consider the following example:
const array = [0, 1, 2, 3, 4, 5, null, undefined];
Let's create an array that excludes only nullish values.
You might prioritize brevity and write it like this:
const numbers = array.filter(Boolean);
Unfortunately, this is not ideal. 0 is also evaluated as false and gets excluded. So you need to write:
const numbers = array.filter(item => item !== null && item !== undefined);
Doesn't this feel like ugly, non-reusable code?
I can write more elegant code:
const numbers = array.filter(checkIsNullish);
Stop writing generic conditions repeatedly. It only leads to mistakes, and the code becomes less readable.
Let me introduce a library I created called checker.
This utility function library represents commonly used conditions in general web development and low-level development as functions. All functions take an input and return a boolean value.
At the time of writing this article, it provides a wealth of functions to handle data types such as strings, numbers, booleans, and nullish values. All functions are tested, documented, and easy to start using.
Let's look at some real-world examples.
The packages provided by this library are all published on JSR. They can be easily installed in NPM, PNPM, Yarn, Bun, and Deno projects.
Here, we'll take the @checker/string package as an example with NPM.
- Install the package
Run the following command in your project directory:
npx jsr add @checker/string
- Using the functions
import { checkIsNotEmptyString, checkIsIndexFound } from "@checker/string"; const value = "Hello"; const formatted = value.trim(); if (checkIsNotEmptyString(formatted)) { // formatted !== '' // When formatted is not an empty string } const index = value.indexOf("el"); if (checkIsIndexFound(index)) { // index !== -1 // When "el" is found in value }
I am not fond of using logical negation operators like !SOME_CONDITION to reverse a boolean value. This is because it's implicit, and simply reversing the boolean value by adding or omitting it can lead to many dangerous situations.
Therefore, all functions have corresponding checkIsNot~ functions defined.
Encapsulate generic conditions in functions. This way, the code becomes more readable, and bugs become easier to spot.
Thank you for reading.
The above is the detailed content of # Replace Generic Validation with Reusable Functions. For more information, please follow other related articles on the PHP Chinese website!

Detailed explanation of JavaScript string replacement method and FAQ This article will explore two ways to replace string characters in JavaScript: internal JavaScript code and internal HTML for web pages. Replace string inside JavaScript code The most direct way is to use the replace() method: str = str.replace("find","replace"); This method replaces only the first match. To replace all matches, use a regular expression and add the global flag g: str = str.replace(/fi

Simple JavaScript functions are used to check if a date is valid. function isValidDate(s) { var bits = s.split('/'); var d = new Date(bits[2] '/' bits[1] '/' bits[0]); return !!(d && (d.getMonth() 1) == bits[1] && d.getDate() == Number(bits[0])); } //test var

This article discusses how to use jQuery to obtain and set the inner margin and margin values of DOM elements, especially the specific locations of the outer margin and inner margins of the element. While it is possible to set the inner and outer margins of an element using CSS, getting accurate values can be tricky. // set up $("div.header").css("margin","10px"); $("div.header").css("padding","10px"); You might think this code is

This article explores ten exceptional jQuery tabs and accordions. The key difference between tabs and accordions lies in how their content panels are displayed and hidden. Let's delve into these ten examples. Related articles: 10 jQuery Tab Plugins

Discover ten exceptional jQuery plugins to elevate your website's dynamism and visual appeal! This curated collection offers diverse functionalities, from image animation to interactive galleries. Let's explore these powerful tools: Related Posts: 1

http-console is a Node module that gives you a command-line interface for executing HTTP commands. It’s great for debugging and seeing exactly what is going on with your HTTP requests, regardless of whether they’re made against a web server, web serv

This tutorial shows you how to integrate a custom Google Search API into your blog or website, offering a more refined search experience than standard WordPress theme search functions. It's surprisingly easy! You'll be able to restrict searches to y

The following jQuery code snippet can be used to add scrollbars when the div content exceeds the container element area. (No demonstration, please copy it directly to Firebug) //D = document //W = window //$ = jQuery var contentArea = $(this), wintop = contentArea.scrollTop(), docheight = $(D).height(), winheight = $(W).height(), divheight = $('#c


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

Dreamweaver CS6
Visual web development tools

Zend Studio 13.0.1
Powerful PHP integrated development environment

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

Atom editor mac version download
The most popular open source editor
