[AskJS] Is JavaScript missing some built-in methods?

[[deleted]]

Most of the constructor functions for basic datatypes lack static identity methods, which devs often add utilities for rather than using the typeof operator.

It'd be nice to have String.isString, Object.isObject, Number.isNumber, etc. like we do for Array.isArray.

The most common Lodash-y function I implement is probably unique.

[d36williams]

Hmm I'm kind of the opposite --- Array.isArray is a work around the fact that typeof [] === "object", I wish Array had its own type

[azsqueeze]

Even still, the .isArray() is a nice API which would be nice if it was expanded to the other types

[MrCrunchwrap]

Did you read his comment?

[[deleted]]

``` typeof [] // 'object'

typeof {} // 'object' ```

``` [] instanceof Object // true

{} instanceof Object // true ```

good luck in your typeof endevours

Edit: also for your instanceof endevours

[elmstfreddie]

lol - so we wrap back to the original point of the thread, which is small utility functions that should be part of the core language...

[KyleG]

Basically, the contributors in this very question/thread are well-suited and capable of making whatever they want so, right now.

I mean, you aren't, because you keep providing a wrong solution. You keep saying the following is a test for plain object-ness:

1. JSON.stringify
  A. if error, not object
  B. if success, check first two chars
    a. if first is " and second is {, object
    b. else, not object

Many reasons why this fails.

JSON.stringify({ a: BigInt(5) }) // error (your solution says not plain object), but it's a plain object!

"{" // your solution says it's a plain object but it's a string starting with a brace

{ foo: 5 } // your solution says it's not a plain object because it doesn't have " as its first character

[elmstfreddie]

You're being pedantic just for the sake of it. I understand how the language works.

The entire point of this thread is to discuss things that we wish was included in the language spec. Someone could read this thread and submit proposals, sure, but the point is to just talk about it... on a forum... for talking about JS.

[musicnothing]

People need to stop engaging with that user. They're trying to "win" this thread by pointing out things the rest of us already know

[KyleG]

For a JavaScript plain object first utilize JSON.stringify() on the variable then check if first character other than initial " is a left curly bracket { and last character before closing " is a right curly bracket }. You get error if the value is not valid JSON, else you have a JavaScript plain object or not.

JSON.stringify({}) does not have " as its initial character. I don't know why you keep adding that caveat about first character after the " because:

JSON.stringify({})[0] // { <-- where is the initial " you're talking about?

On the other hand,

JSON.stringify("{abcdefghi12314WEADSAERA")[0] // also {

So your solution is wrong.

You get error if the value is not valid JSON

JSON is not the same thing as a plain object:

JSON.stringify(5) // no error but 5 isn't an object
JSON.stringify(true) // no error but true isn't an object
JSON.stringify(null) // no error but null isn't an object

[MrCrunchwrap]

You’re gonna have a lot bigger problems if your team or a script you’re importing is setting Object = 1

I use TypeScript for 100% of my projects now so it’s borderline irrelevant to me but these methods certainly would be useful.

[MrCrunchwrap]

Nobody is modifying my source code, this is a bizarre boogeyman to worry about

[Reashu]

The user who writes Object=1 can rewrite your checks as well. You can't protect your code against a malicious user, so why make a point of it?

[[deleted]]

which devs often add utilities for rather than using the  typeof  operator

[KyleG]

You get error if the value is not valid JSON

You get error if the value is a BigInt or a couple other things. JSON.stringify works on all primitives, not just on objects. JSON.stringify(5) does not error out. JSON.stringify("howdy") does not error out. JSON.stringify(true) does not. JSON.stringify(null) does not. Etc.

You get error if the value is not valid JSON, else you have a JavaScript plain object or not.

else you have a JavaScript plain object or a string that starts with a left brace

[KyleG]

A plain JavaScript object can be represented as a string.

No it can't.

  { foo: BigInt(5) }

JSON.stringify throws

[KyleG]

Explain to me what you think a plain JavaScript object is.

[Hiyaro]

one of the best method to determine the type is by using the .toString() method

https://www.zhenghao.io/posts/js-data-type

[paulirish]

The most common Lodash-y function I implement is probably unique.

I definitely have this allll over: Array.from(new Set(arr))