How to Fix "replaceAll is not a function" Errors in JS

Learn what is the root cause and how you can fix "replaceAll is not a function" errors in JavaScript.

Ferenc Almasi • 2022 November 10 • 📖 1 min read

How to Fix "serializes to the same string" Errors in Jest

Learn how you can fix "serializes to the same string" errors in Jest using the correct matchers for expect statements.

Ferenc Almasi • 2022 November 08 • 📖 1 min read

How to Properly Pass Params to on:click in Svelte

Learn how you can properly pass parameters to function calls inside on:click event handlers in Svelte

Ferenc Almasi • 2022 October 28 • 📖 2 min read

Fix "cannot read properties of null (reading length)" in JS

Learn what is the cause, and how you can fix 'Uncaught TypeError: Cannot read properties of null (reading 'length')' errors in JavaScript.

Ferenc Almasi • 2022 October 15 • 📖 3 min read

Two Ways to Get Enum Keys by Values in TypeScript

Learn how you can get enum keys by their values in TypeScript using two different methods.

Ferenc Almasi • 2022 September 28 • 📖 2 min read

How to Extend Multiple Classes in TypeScript With Mixins

Learn how you can get around extending multiple classes in TypeScript using a mixin.

Ferenc Almasi • 2022 September 26 • 📖 2 min read

Two Ways to Force Types in TypeScript

Learn how you can force types in TypeScript using two different syntaxes.

Ferenc Almasi • 2022 September 26 • 📖 2 min read

How to Easily Extend Interfaces in TypeScript

Learn how you can extend your interfaces in TypeScript with other interfaces.

Ferenc Almasi • 2022 September 23 • 📖 3 min read

How to Correctly Check Undefined in TypeScript

Learn how you can correctly check if your variables are undefined in TypeScript.

Ferenc Almasi • 2022 September 21 • 📖 2 min read

Extending Types in TypeScript The Right Way

Learn how you can extend types in TypeScript using the & operator.

Ferenc Almasi • 2022 September 20 • 📖 2 min read

3+1 Ways to Declare Global Variables in TypeScript

Learn what are the different ways to declare global variables in your TypeScript app.

Ferenc Almasi • 2022 September 20 • 📖 3 min read

How to Check Variable Types in TypeScript

Learn how you can check the type of your variables in TypeScript with the typeof and instanceof keywords.

Ferenc Almasi • 2022 September 19 • 📖 3 min read

4 Ways to Convert Strings to Booleans in TypeScript

Learn what are the different ways to convert strings to boolean in Typescript in a type-safe way.

Ferenc Almasi • 2022 September 19 • 📖 4 min read

Why You Should Not Use Classes in React Testing Library

Learn why you should not be using class names in React Testing Library for querying your elements.

Ferenc Almasi • 2022 September 16 • 📖 3 min read

How to Fix "React Hook is Called Conditionally" Errors

Learn how you can resolve "React hook is called conditionally" error messages in your React app.

Ferenc Almasi • 2022 September 15 • 📖 3 min read

What Should You Use Instead of QuerySelector in React

Learn how should you work with document.querySelector properly inside React.

Ferenc Almasi • 2022 September 14 • 📖 3 min read

How to Test Component Functions In React Testing Library

Learn how you can properly test functions inside your component in React Testing Library.

Ferenc Almasi • 2022 September 14 • 📖 3 min read

How to Get All Form Values on Submit in React

Learn how you can properly grab all form data at once in React using a state object with useState.

Ferenc Almasi • 2022 September 13 • 📖 8 min read

How to Easily Pass Data From Child to Parent in React

Learn how you can easily pass state and data from your child components to your parent components in React.

Ferenc Almasi • 2022 September 13 • 📖 3 min read

How to Get Rid of Bullet Points in CSS

Learn how you can properly get rid of bullet points from your list items in CSS using the list-style-type property.

Ferenc Almasi • 2022 September 13 • 📖 2 min read

Exclude Any Class Name in CSS With This Selector

Learn how you can exclude any selector in CSS using the :not pseudo class.

Ferenc Almasi • 2022 September 12 • 📖 2 min read

How to Disable Text Selection in CSS Using One Rule

Learn how you can use the user-select property in CSS in order to prevent users to select certain elements on the page.

Ferenc Almasi • 2022 September 12 • 📖 1 min read

How to Refresh Pages in React With One Line of Code

Learn how you can properly trigger a page refresh in React with one line of code.

Ferenc Almasi • 2022 September 12 • 📖 1 min read

How to Properly Use setTimeout in React

Learn what is the proper way to use setTimeout inside your React components

Ferenc Almasi • 2022 September 09 • 📖 4 min read

3 Ways to Get Query Params in React (Without Router Too)

Learn how you can access query params in your React components in React Router v6, v5, and without using React Router.

Ferenc Almasi • 2022 September 09 • 📖 2 min read

Disabling Buttons in React Based on Input Fields

Learn how you can properly disable and enable buttons in React based on the value of other input fields.

Ferenc Almasi • 2022 September 08 • 📖 2 min read

How to Test onChange Events in React Testing Library

Learn how you can properly test the onChange event of your components in React Testing Library.

Ferenc Almasi • 2022 September 04 • 📖 2 min read

Testing Disabled Buttons in React Testing Library

Learn how you can properly test whether your buttons or disabled or enabled in React Testing Library.

Ferenc Almasi • 2022 September 04 • 📖 1 min read

Properly Testing Button Clicks in React Testing Library

Learn how you can properly test button clicks in React Testing Library to test your UI events.

Ferenc Almasi • 2022 September 03 • 📖 1 min read

How to Fix "Functions are not valid as React child" Errors

Learn what is the root cause, and how to fix "Functions are not valid as React child" errors in your React app.

Ferenc Almasi • 2022 July 25 • 📖 2 min read

How to Fix "JSX element must be wrapped in enclosing tag"

Learn what is the root cause and how to fix "Adjacent JSX elements must be wrapped in an enclosing tag" errors in your React app.

Ferenc Almasi • 2022 July 25 • 📖 3 min read

How to Fix " Received false for non-boolean attribute" Errors

Learn what is the root cause, and how to fix "Warning: Received false for a non-boolean attribute className." warnings in React.

Ferenc Almasi • 2022 July 25 • 📖 1 min read

How to Fix "Each child should have a unique key prop"

Learn what is the root cause, and how to fix "Warning: Each child in a list should have a unique "key" prop." warnings in your React app.

Ferenc Almasi • 2022 July 22 • 📖 2 min read

How to Send Query Params in GET and POST in JavaScript

Learn how you can send query parameters in your GET and POST in JavaScript, and how to create helper functions for reusing them.

Ferenc Almasi • 2022 July 21 • 📖 4 min read

How to Create Associative Arrays in JavaScript

Learn what are associative arrays, and how they can be created and used in JavaScript in place of regular arrays.

Ferenc Almasi • 2022 July 20 • 📖 2 min read

How to Fix "Maximum call stack size exceeded" Errors in JS

Learn what is the root cause and how you can fix "Uncaught RangeError: Maximum call stack size exceeded" errors in JavaScript.

Ferenc Almasi • 2022 July 17 • 📖 2 min read

How to Fix "Nothing to repeat" Errors in JavaScript

Learn what is the root cause and how you can fix "Uncaught SyntaxError: Nothing to repeat" errors in JavaScript.

Ferenc Almasi • 2022 July 16 • 📖 2 min read

How to Fix "cannot set properties of null" Errors in JS

Lear what is the root cause and how you can fix "Uncaught TypeError: Cannot set properties of null (setting 'value')" errors in JavaScript.

Ferenc Almasi • 2022 July 14 • 📖 3 min read

How to Fix "Illegal return statement" Errors in JavaScript

Learn what is the root cause of and how to fix "Uncaught SyntaxError: Illegal return statement" errors in your JavaScript code.

Ferenc Almasi • 2022 July 12 • 📖 3 min read

How to Fix "illegal character u+" Errors in JavaScript

Learn what is the cause, and how you can fix "Uncaught Syntaxerror: illegal character u+" errors in JavaScript.

Ferenc Almasi • 2022 July 12 • 📖 2 min read

How to Fix Uncaught URIError: URI malformed Errors in JS

Learn what is the root cause, and how can you fix "Uncaught URIError: URI malformed" errors in your JavaScript code.

Ferenc Almasi • 2022 July 11 • 📖 2 min read

Fix "cannot read properties of undefined (reading map)" in JS

Learn what is the cause, and how you can fix "Uncaught TypeError: Cannot read properties of undefined (reading 'map')" errors in JavaScript.

Ferenc Almasi • 2022 July 11 • 📖 2 min read

Fixing "Delete of an unqualified identifier" Errors in JS

Learn how to easily fix "Uncaught SyntaxError: Delete of an unqualified identifier in strict mode." errors in JavaScript.

Ferenc Almasi • 2022 July 11 • 📖 2 min read

How to Fix "$ is not defined" Errors in JavaScript

Learn what causes "Uncaught ReferenceError: $ is not defined" errors in JavaScript, and how you can fix them in various ways.

Ferenc Almasi • 2022 July 10 • 📖 3 min read

How to Fix "Unexpected token o in JSON at position 1"

Learn how you can fix uncaught syntaxerror unexpected token o in json at position 1 errors in JavaScript, and what is the root cause of this error.

Ferenc Almasi • 2022 July 09 • 📖 3 min read