Podcasts Technology Syntax - Tasty Web Development Treats New to JavaScript ES2022

New to JavaScript ES2022

Published: Sept. 15, 2021, 1 p.m.

In this episode of Syntax, Scott and Wes talk about all the new stuff in ES2022 \u2014 what it is, why you might need it, and how to use it.

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Show Notes

04:50 - Regex indicies

  • New\xa0d\xa0flag 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\xa0#
  • =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\xa0static 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\xa0in\xa0keyword

16:00 -\xa0.at()\xa0method

  • Strings and arrays - we can use square brackets to reference items of the array
  • Super handy for grabbing the last item of an array
 // \U0001f525 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\xa0hasOwn\xa0method

24:51 - Class static block

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