Author: Mark

  • Copying a state variable’s value

    To copy the value of a variable declared using useState, if it’s an array use: let varName = […stateVar]; If it’s not an array use: let varName = stateVar.valueOf();

  • Creating an array of empty arrays

    If you do: let arr = new Array(5); arr.fill([]); This will make an array of 5 identical arrays where editing one will update all which is rarely what anyone wants. To achieve an array of different arrays use: let arr = Array.from(new Array(5), () => [])

  • Update all dependencies in package.json to latest

    To do this, use npm-check-updates Install with Then update with

  • Accessible hash links

    This is mainly for the ‘skip to content’ links. $(“a[href^=’#’]”).not(“a[href]=’#'”).click(function() {    $(“#”+$(this).attr(“href”).slice(1)+””).focus(); });

  • Difference between var, let and const

    var declarations are globally scoped or function scoped while let and const are block scoped. This means you can declare the a let or const with the same name inside an if statement and it will be self contained. The console would log “aa bb” followed by “a b”. Let and const can’t be redeclared in…

  • Difference between document.ready and window.onload

    Triggers when the HTML is ready. Use this to start running code as soon as possible. This is not jQuery. Trigger when everything on the page (eg images) is finished loading.

  • CSS Modules

    CSS modules allow you to create unique class names even when the class is already used in another file. Name the file like so: name.module.css. Right normal css in it. Import the file like so: Apply it to an element like so: where testClass is a class specified in your css module file. When the…

  • Passing a function prop from child to parent

    Using the same example as passing a function from parent to child but going in the opposite direction. Here the parent has a callback function and passes it to the child component. The child calls the callback with it’s own function as the argument. As before you can use the component like so:

  • Passing a function prop from parent to child

    We have a Parent component that contains the child component “ChildBtn”. Parent has the function parentFunction which is passed into the child. We can also specify the console log text and the button text. We can then use the component like so:

  • JQuery scrolling logic