> Le 13 oct. 2016 à 19:20, Bob Myers <r...@gol.com> a écrit :
>
> Why is this needed? Why are people trying to get the property of an object
> which is null? Why is the object null in the first place?
This is not about trying to get something from null, but about taking different
paths according to when a reference is null or not without needing to assign to
temporary variables, writing complete `if` structures, and/or repeating oneself.
> (...)
>
> Just as an example, consider the following idiom for null propagation:
>
> ```
> a ? a.b ? a.b.c : undefined : undefined
> ```
>
> We can leverage this pattern by allowing the `:` in the ternary operator to
> be omitted (defaulting to undefined), allowing us to write:
>
> ```
> a ? a.b ? a.b.c
> ```
>
> Whether you love it or hate it, at least this solves more problems that just
> null propagation. I'm not seriously suggesting this. I'm just saying we need
> to be more creative in brainstorming possible solutions to the problem.
You can already write`a && a.b && a.b.c` in JS... but you still have to repeat
`a` thrice and`b` twice, which is an issue if `a` and `b` are complex or
lengthy expressions. Sometimes I am tempted to write something in the lines of
`(_ = a.b) && _.c` in order to avoid the issue, but it is less readable.
Here is a more complex although somewhat contrived example: If an <input>
element named "foo" is inside a <details> section, open the latter in order to
reveal the former:
```js
document.querySelector("input[name=foo]")?.closest(".details")?.open = true
```
(The short-circuiting mechanism, which is an important part of the semantics in
my proposal, ensures that the assignment is performed only when the expressions
just before the `?`s are not null/undefined.)
—Claude
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