To filter an array of objects by multiple properties in TypeScript, combine the tests inside one predicate: orders.filter(o => o.status === “shipped” && o.city === “Austin”) for “all of these”, and || for “any of these”. That covers two fixed conditions. Real screens need more: several selected values for the same field, ranges, a search … Read more >>
React prints this warning when one component changes another component’s state while it is rendering. Depending on your React version the text is either “Cannot update a component (Parent) while rendering a different component (Child)” or the older “Cannot update a component from inside the function body of a different component”. Both mean the same … Read more >>
You cannot use React hooks inside a class component. Hooks only work in function components and in custom hooks, and React throws an error if you call one from a class. There are three practical ways round it: wrap the class in a small function component that calls the hook and passes the values down … Read more >>
A Gantt chart shows tasks as bars on a timeline, with dependencies between them. In React you have two sensible routes: install a library, or build a small chart yourself with CSS grid. This guide does both. The library part uses gantt-task-react, which is free, MIT-licensed, and gives you dependency arrows, drag and resize, progress … Read more >>
To filter an array of objects in TypeScript, pass filter() a function that tests a property: orders.filter(order => order.status === “shipped”). You get a new array of the same object type, the original is untouched, and the compiler checks every property name as you type it. This guide covers filtering by one property and by … Read more >>
react-vertical-timeline-component renders a vertical timeline in React: a centre line with cards alternating left and right, each with a date and an icon. You install it, import its stylesheet, and put a <VerticalTimelineElement> inside a <VerticalTimeline> for every event. This guide builds one step by step, with a screenshot of what each version actually renders, … Read more >>
Python has two division operators. / is true division and always returns a float, so 7 / 2 is 3.5 and even 8 / 4 is 2.0. // is floor division: it divides and then rounds down, so 7 // 2 is 3. The difference that catches people out is negative numbers, where -7 // … Read more >>
Python has no built-in repeat() function, and what you need depends on what you are repeating. To repeat code a fixed number of times, use for _ in range(n). To repeat it until something happens, use while True with a break, because Python has no repeat-until loop. To repeat a value, multiply it: “ab” * … Read more >>
A React date picker component gives users a calendar to choose a date from instead of a free-text field. You have two realistic options: the browser’s own <input type=”date”>, which costs nothing and looks different in every browser, or the react-datepicker library, which is the one most projects mean when they say “React date picker”. … Read more >>
The Python ceil() function rounds a number up to the nearest whole number. It lives in the math module, so you call it as math.ceil(x) after import math: math.ceil(2.1) gives 3, and math.ceil(-2.8) gives -2, because up means towards positive infinity. It always returns an int, never a float. This guide covers the ceiling function … Read more >>