In JavaScript, do there exist any ways to get a property of an object without using dot notation or bracket notation?

Question

Let's say I have a simple object a = {b: 2}. I know of two ways to get the value of property b of a:

Dot notation: a.b // 2

and

Bracket Notation: a['b'] // 2

Practicality aside, does there exist any way to get the value of b from object a without using either of these two methods (dot notation and bracket notation)? MDN's page on Property Accessors only lists the 2 methods.

It's just a curiosity I had. I know there exist obscure ways to call functions without parenthesis, eg

parseInt`5.1`

I wanted to see if a similarly obscure thing was possible for Property access.

It depends upon what you are trying to do. For example, in your limited example `a[0] //2` as well. — Sablefoste, Sep 21 '18 at 01:39
@phil, right, it gives `undefined`. But also the point is it could be used in a reference. For example: https://stackoverflow.com/a/24061635/1408137 — Sablefoste, Sep 21 '18 at 01:49
@Phil It's just a curiosity I had. I know there exist obscure ways to call functions without parenthesis (ex. double backticks). I wanted to see if a similarly obscure thing was possible for Property access. — Lucien, Sep 21 '18 at 01:56
You should probably explain that in your question. Right now, it just seems pointless since brackets and dots work just fine. Also, what's this double-backtick syntax you speak of? — Phil, Sep 21 '18 at 01:57
Don't overlook the power of bracket notation, though. There is so much that can be accomplished with that feature. — Ben Steward, Sep 21 '18 at 02:02
@phil My favorite example of how weird javascript is involves backticks: `Function\`$${\`alert($$)\`}$$\`\`$${\`wat\`}$$\`` — Lucien, Sep 21 '18 at 02:04
This is hilarious; I don't think there is a reason, but a definitive reference may be helpful for someone??? — Rafael, Sep 21 '18 at 02:18
@Rafael Are you talking about the alert statement? Because if so, I'd be happy to explain how it works! Although the comment section might not leave enough space. — Lucien, Sep 21 '18 at 02:45

Phil · Answer 1 · 2018-09-21T02:00:50.650

3

First thing that springs to mind is Object.values

const a = {b: 2}

Object.values(a).forEach(v => {
  console.info(v)
})

But how would you know what key you're accessing?

There's also Object.entries() I suppose

const a = {b: 2}

Object.entries(a).forEach(entry => {
  // entries are [key, value] arrays
  let value = entry.pop()
  let key = entry.pop()
  console.info(key, ':', value)
})

Note: I used Array.prototype.pop() so as not to use "bracket notation".

edited Sep 21 '18 at 02:00

answered Sep 21 '18 at 01:39

Phil

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Nothing prompts creativity quite like a restriction. – Ben Steward Sep 21 '18 at 01:58

score 3 · Accepted Answer · answered Sep 21 '18 at 01:43

3

This is not exactly the same as accessing a property, but it’s nevertheless a sneaky way to get at an object’s contents if you are using the latest JS (es6+). All the hip JS kids are doing it these days.

const { b } = a
console.log(b) // 2

This is called destructuring, it works with objects and arrays, and you can read more about it here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment

answered Sep 21 '18 at 01:43

Ben Steward

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And here I am using functions like some kind of grandpa. Nice answer :D – Phil Sep 21 '18 at 01:55
Both answers are really insightful, but I'll accept this one since it avoids using any dot syntax or bracket notation entirely. Now I wonder if there is a way to use destructuring if we can't type the variable name directly, but rather have a string with its name. Like: `const a = {b: 2}; const c = 'b'; // somehow access b using destructuring using the variable c`. Interesting stuff to consider. Anyway, thanks! – Lucien Sep 21 '18 at 02:10
@Lucien you sure can... `let { b: c } = a`. This is handy for property names that don't make good variables, eg `{ '.id': 2 }`. Edit: I may have misunderstood – Phil Sep 21 '18 at 02:26
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These are the droids you are looking for: https://tylermcginnis.com/videos/computed-property-names/ – Ben Steward Sep 21 '18 at 02:29

score 2 · Answer 3 · answered Sep 21 '18 at 02:14

Don't forget Object.getOwnPropertyDescriptor():

const object1 = {
  property1: 42
}

const descriptor1 = Object.getOwnPropertyDescriptor(object1, 'property1');
console.log(descriptor1.value);//42

It doesn't search through the prototype chain, but it works on immediate properties and worth noting, for you can make recursive functions searching the prototype chain with it :)

In JavaScript, do there exist any ways to get a property of an object without using dot notation or bracket notation?

3 Answers3