3 ms·

But lists are objects, with negative indices as possible keys: > const l = [1,2,3]; undefined > l.a = l; [ 1, 2, 3, a: [Circular] ] > l ===

by ulucs 6y ago

But lists are objects, with negative indices as possible keys: > const l = [1,2,3]; undefined > l.a = l; [ 1, 2, 3, a: [Circular] ] > l === l.a true > l[-1] = 0; 0 > l [ 1, 2, 3, a: [Circular], '-1': 0 ]

Silhouette 6y ago
Even without that argument, the behaviour is still consistent with other cases for arrays in JS anyway. > const a = [1, 2]; > a[0] 1 > a[2] undefined > a[-1] undefined
robertlagrant 6y ago
And positive indices not as possible keys, but as array elements. It's crazily inconsistent. > l = [1,2,3] (3) [1, 2, 3] > l[3] = 4 4 > l (4) [1, 2, 3, 4] > l[-1] = "eek" "eek" > l (4) [1, 2, 3, 4, -1: "eek"] So adding a 4 as a "key" is a proper array element; adding -1 is an object key. I'm struggling to see how anyone could think this is a good idea. Saying that they're objects is not reasonable. Objects don't need to do this (in most languages lists are objects, and they don't also do key-value pairs at the same time); they just decided to make them do this.
- qsort 6y ago
  It's extremely consistent. I'd say that's the only consistent way to do it, if you want to preserve the semantics of JS objects. Lua does pretty much the same. > Saying that they're objects is not reasonable. This is a fair point, in the alternate universe where JS objects have different semantics. > in most languages lists are objects, and they don't also do key-value pairs at the same time This is a dynamic language we're talking about. You are very welcome to think dynamic languages are inferior choices, an opinion that I personally would share, but that's a discussion for another time. In the context of JS, that behavior is neither unreasonable nor inconsistent.
  - robertlagrant 6y ago
    Python is also dynamic. That has nothing to do with this. >>> l = [] >>> l.x = "hello" Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: 'list' object has no attribute 'x' Always adding arbitrary properties to an object is not a dynamic thing, it's just a bit silly. At best you could say it's a weak typing thing, but even then, it doesn't need to be.

by ulucs 6y ago

Silhouette 6y ago

Even without that argument, the behaviour is still consistent with other cases for arrays in JS anyway. > const a = [1, 2]; > a[0] 1 > a[2] undefined > a[-1] undefined

robertlagrant 6y ago

And positive indices not as possible keys, but as array elements. It's crazily inconsistent. > l = [1,2,3] (3) [1, 2, 3] > l[3] = 4 4 > l (4) [1, 2, 3, 4] > l[-1] = "eek" "eek" > l (4) [1, 2, 3, 4, -1: "eek"] So adding a 4 as a "key" is a proper array element; adding -1 is an object key. I'm struggling to see how anyone could think this is a good idea. Saying that they're objects is not reasonable. Objects don't need to do this (in most languages lists are objects, and they don't also do key-value pairs at the same time); they just decided to make them do this.

qsort 6y ago
It's extremely consistent. I'd say that's the only consistent way to do it, if you want to preserve the semantics of JS objects. Lua does pretty much the same. > Saying that they're objects is not reasonable. This is a fair point, in the alternate universe where JS objects have different semantics. > in most languages lists are objects, and they don't also do key-value pairs at the same time This is a dynamic language we're talking about. You are very welcome to think dynamic languages are inferior choices, an opinion that I personally would share, but that's a discussion for another time. In the context of JS, that behavior is neither unreasonable nor inconsistent.
- robertlagrant 6y ago
  Python is also dynamic. That has nothing to do with this. >>> l = [] >>> l.x = "hello" Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: 'list' object has no attribute 'x' Always adding arbitrary properties to an object is not a dynamic thing, it's just a bit silly. At best you could say it's a weak typing thing, but even then, it doesn't need to be.