primitive wrapper objects cause unexpected behavior

[dwhieb]

javascript/src/models/Language.js

Line 107 in 12f0a50

this.#abbreviation = new String(val);

Describe the bug
Using a primitive wrapper object (new String) here causes unexpected behavior, because unlike normal instantiation of primitives, the wrapper object is not discarded after instantiation. In the code above, typeof this.#abbreviation will yield object rather than string.

Fix
The above code should either be converted back to the primitive value this.#abbreviation = (new String(val)).valueOf(), or just removed this.#abbreviation = val;. Probably the latter.

Reference

• https://developer.mozilla.org/en-US/docs/Glossary/Primitive#Primitive_wrapper_objects_in_JavaScript
• https://programmingwithmosh.com/javascript/javascript-wrapper-objects/

[dwhieb]

[javascript] remove primitive wrapper objects

[dwhieb]

@vadekh My brain kept drifting back to this issue, and I finally realized why. I remembered that previously I had read that it's a great idea to use primitive object constructors like String() and Number() when doing type conversions because it makes the conversion explicit, and I even remembered doing this in previous projects. But I also remembered the various unexpected side effects of using primitive object wrappers, like the ones we ran into in our code. What I forgot is that there's a difference between new String(), which creates a new primitive object wrapper and returns an Object, and just String(), which is explicitly designed to do type conversion:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/String

Let's update our codebase so that we use String() etc. wherever we're doing explicit type conversion. There are probably multiple places in our code this would be applicable to now.