Any help please?

Question

https://www.sololearn.com/post/99607/?ref=app

Also why its 4
https://www.sololearn.com/post/99613/?ref=app

Answer 1

Hafsa Hussein Mohammed I agree with the explanations provided by ~ swim ~ and Gordon.

Recapping Problem 1:

By default, in Javascript, the context of `this` belongs to the relative parent scope from where the function is invoked.

var go = fun.day.bar;

Here, the relative parent scope of the variable `go` will be different from that of `bar` and will be reflected as such when invoking the respective functions.

Therefore, `go()` will access the value `x` defined in its relative parent, the global scope, which is 3.

Likewise, when calling `fun.day.bar()`, the relative parent is the `day` object, where the value `x` is 1.

(continue...)

Answer 2

Gordon I saw that too. But, I assumed Javascript will cast it to number.

¯\_(ツ)_/¯

Answer 3

The all game is of 'this' keyword.
When you store the function 'bar' , in 'go' variable of window object, the 'this' object will hold the window object. Then you know,
var x = 3
console.log(window.x==x);
Inside go function, this==window
So, this.x==x.

I think the remaining part of explanation, you can imagine, think yourself.

Gordon
David Carroll
~ swim ~
I properly agreed to your answer.

Answer 4

SPACE David Carroll Gordon ~ swim ~ thanks all for the helpful answers

Answer 5

Recapping Problem 2:

A new, readonly property named `-1` is defined on `Array.prototype`. The getter for this new property returns the last index position of the current array instance.

An easier way to read this would be to replace `-1` with "lastValue" in this code.

Then the code would make more sense where either of the following lines would return 4:

//Property accessor via key.
//Same as `a[-1]`
a["lastValue"]

//Property accessor via dot notation.
a.lastValue

NOTE: No equivalent exists for the second example since `a.-1` is invalid. Properties cannot be accessed via the dot notation if their name begins with a numeric or operator character. Therefore, only the key accessor is valid.

Answer 6

Gordon David Carroll

Answer 7

Question 2
- Array is a type of Object
- We can use square bracket as well as dot to access Object property
- define property defines the getter of -1 in a Python-alike manner, returning the last element in an array.
https://www.sololearn.com/post/46592/?ref=app
https://code.sololearn.com/Wyr76080kKxS/?ref=app

Answer 8

Closures
https://www.sololearn.com/post/91113/?ref=app

swim's right

Answer 9

David Carroll

funny thing is happening in [] 🧐
https://code.sololearn.com/WBqcWEVjEJ3z/?ref=app

i can arr["0"] 🤔

i guess you are right, "-1" is treated as -1

Answer 10

i just found this experiment of define getter by SPACE
https://code.sololearn.com/WgqQ01BXR3Db/?ref=app

doing something similar, just using another syntax

Answer 11

for getter setter, this is simple and clear demo
https://code.sololearn.com/WuswYAzn9MWs/?ref=app

Answer 12

This demo is "array is a type of object"
https://code.sololearn.com/WdpzC6Y7zBa6/?ref=app

Answer 13

in question 2,

come to think of it, in defineProperty, it's "-1" (a string), but in accessing, it's -1 (int),

so what's the underlying typecast? int to string or string to int? when did it happen?

Answer 14

https://code.sololearn.com/WrEh9t4MT7g3/?ref=app