This is a personal collection where I jot down things I don't know and briefly summarize what I learn about them. If you know the answer to any of the unanswered questions, please leave a comment. Thank you.
Full Q&A List
[Answered]
1. What is This is a ${msg}?
This is a new string notation added in ES6, called a Template Literal. Template literals allow line breaks within a string without using the \ character, and they let you easily substitute the value of a variable directly through the simple ${…} string interpolation expression.
References
- https://poiemaweb.com/es6-template-literals
- https://developer.mozilla.org/ko/docs/Web/JavaScript/Reference/Template_literals
2. What is the difference between var, const, and let?
The const and let keywords were introduced in ES6.
-
var * the scope works at the function level
-
const
- the scope is block-level
- used when the value does not change
-
let
- the scope is block-level
- used when the value changes
References
3. What does () => ({}) mean in lambda expression form?
ES6 added lambda expression syntax. The expression () => ({}) is equivalent to function() { return { } }.
References
4. What is …?
This is syntax added in ES6 that can be used as a Spread or a Rest Parameter.
-
Spread operator
- expands an iterable array, object, or string into individual elements
- ex.
-
Rest Parameter
- collects all elements into an array
- the Rest Parameter must be the last argument
References
- https://developer.mozilla.org/ko/docs/Web/JavaScript/Reference/Functions/rest_parameters
- https://scotch.io/bar-talk/javascripts-three-dots-spread-vs-rest-operators543
- https://jaeyeophan.github.io/2017/04/18/ES6-4-Spread-Rest-parameter/