New to JavaScript — ES2022

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By Wes Bos and Scott Tolinski - Full Stack JavaScript Web Developers. Discovered by Player FM and our community — copyright is owned by the publisher, not Player FM, and audio is streamed directly from their servers. Hit the Subscribe button to track updates in Player FM, or paste the feed URL into other podcast apps.

In this episode of Syntax, Scott and Wes talk about all the new stuff in ES2022 — what it is, why you might need it, and how to use it.

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Show Notes

04:50 - Regex indicies

  • New d flag in a regex
  • https://regex101.com/
  • This will tell you the indexes (indicies) of the regex matches
  • Handy if you need to highlight or replaces matches in a string
  • We can ask for the start and end positions of each matched capture group

07:16 - Class updates

  • Private fields
  • Properties and Methods to be kept private
  • Prefix them with a #
  • =Helpful for internal state and methods which should not be accessed directly or at all by external
  • In React how we have __INTERNTAL_NEVER USE THIS
class ColorButton extends HTMLElement { // All fields are public by default color = "red" // Private fields start with a #, can only be changed from inside the class #clicked = false } const button = new ColorButton() // Public fields can be accessed and changed by anyone button.color = "blue" // SyntaxError here console.log(button.#clicked) // Cannot be read from outside button.#clicked = true // Cannot be assigned a value from outside class Person { #hobbies = ['computers'] get #hobbiesGetter() { return this.#hobbies } #getHobbies() { return this.#hobbies } getHobbiesPublic() { return this.#hobbies } } const scott = new Person(); scott.#getHobbies(); // doesn't work scott.getHobbiesPublic(); // works

09:07 - Class fields

  • This may seem super old because we have been polyfilling it forever
  • Right now if you want an instance field on a class, you need to declare it in the constructor
  • Now we can just declare them inside the class

10:36 - Static fields and methods

  • As above can also be static with the static keyboard
  • Works for methods too
    • Explain what a static method is

13:17 - Top level await

  • So handy in modules. Need to pull in some data? Simple.

15:19 - Ergonomic brand checks for private fields

  • Used for checking if a private field on a class exists using the in keyword

16:00 - .at() method

  • Strings and arrays - we can use square brackets to reference items of the array
  • Super handy for grabbing the last item of an array
// 🔥 New .at() method on arrays and strings const toppings = ['pepperoni', 'cheese', 'mushrooms']; // The old way to grab the last item toppings[toppings.length - 1]; // mushrooms // using .at() method with a negative index toppings.at(-1); // mushrooms // works with any index toppings.at(0); // pepperoni toppings.at(-2); // cheese // and with strings! 'Meeting Room: B'.at(-1) // B
  • Why not use array[-1]?
  • We used to use slice(-1)
  • What about indexOf?

21:34 - Handy hasOwn method

24:51 - Class static block

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