in operator (JS)

It’s easy to get started at JS, also very easy to make bugs. It may be due to our prejudice or may be JS’s fault. At the end of the day I have to write js, As I have no other choice at my work.

What happened

So breif of what happened today. My task was to check if a string exists on array of strings. coming from a python background, I thought of using in operator.

`'hello' in ['hi', 'hello']`. # true

I know there is in operator in JS. So I assumed it should be like checking if a value exists in a iterable.(Yep my bad, I assumed).
To quickly verify my assumption, I tried following code snippet in node

1 in [1, 2, 3, 4] // true

I was happy and without any second thoughts I used that on my original problem. But it failed. Wait what? So as usual I did goto holy JS docs website mdn

in Operator in JS

The in operator returns true if the specified property is in the specified object or its prototype chain.

Why did my node snippet worked?
why not, array is object, and index are property. So js compiler wasn’t looking for value 1, It was checking for if there is index 1.

What’s weird?

JS land makes be very uncomfortable. If I get a chance I will escape and will never come here :p

let trees = new Array('redwood', 'bay', 'cedar')
delete trees[0]

for (let tree of trees)
    console.log(tree);

// undefined
// bay
// cedar

When we delete a val from array, we need to move other elements to the front right. Not necessarily, but plebeian in like me was exepecting that. May be JS is for far superior people with less prejudice. (I should move to rust)