(re)studying javascript

• Have read the latest edition of "Learning javascript" at least three times.
• Have read "You Don't Know JS" at least once
• Have coded substantial amount of javascript already
• Now wanting to get some really fine techniques on javascript

Read Airbnb's javascript style guide:

• ⌛: 30 ~ 60 mins
• From 1. Types
• To 7.6 Never use arguments, opt to use rest syntax ...

The slice() method returns a shallow copy of a portion of an array into a new array object selected from begin to end (end not included). The original array will not be modified.

• Q: slice works on objects?
• A: Slice method can also be called to convert Array-like objects / collections to a new Array.. So you could do something like:

  const info = Array.prototype.slice.call({0: "Korea", 1: "KST", length: 2}) // ["Korea", "KST"]

  Remember you need to specify the length, and the object keys should be indices. The following would result in nothing but an empty array:

  const info = Array.prototype.slice.call({home: "Korea", time: "KST"}) // []

  But anyways, it's not recommended to use Array.prototype.slice, but Array.from.

• Q: So what can Array.from actually do with mapping?
• A: This:
  Array.from can receive a mapping function as the second argument, as such:

  const mapped = Array.from([1,2,3], elem=>elem*2) // 2,4,6

Read Airbnb's javascript style guide:

• ⌛: 30 ~ 60 mins
• From 7.7 Use default parameter syntax...
• To 15.5 Use braces to create blocks in case and default clauses...

1. 14.2 Anonymous function expressions hoist their variable name, but not the function assignment.
2. 14.3 Named function expressions hoist the variable name, not the function name or the function body.

Read Airbnb's javascript style guide:

• ⌛: 45 ~ 60 mins
• From 15.6 Ternaries should not be nested...
• To 30.2 No, but seriously: (The end)

• 18.4 You can use FIXME or TODO to annotate something in the comment.
• 19.6 Use indentation when making long method chains...
• 21.1 Use semicolons.: You know, I don't really use semicolons in Javascript because the code tends to look cleaner. But airbnb certainly has suggested possible grounds for this, such as:
  • "rules will become more complicated as new features become a part of JavaScript. Explicitly terminating your statements and configuring your linter to catch missing semicolons will help prevent you from encountering issues."
  • But doesn't prettier do the job for filling out all the semicolons? I will have to dig into this a bit more.
• 22.2 Type casting for strings: don't use new keyword, but just 'String', because using the new keyword will let javascript recognize the variable as an object. (typeof)
• 23.4 Do not use trailing or leading underscores.
• 25.1 When attaching data payloads to events (whether DOM events or something more proprietary like Backbone events), pass an object literal (also known as a "hash") instead of a raw value.
• 29.1 Use Number.isNaN instead of isNaN (same for Number.isFinite)