On 9/13/17 9:57 AM, Naveen Chawla wrote:
By this behaviour (a modification to the initial "complete statement
produces comma" version of this proposal), everything would work
perfectly, no?
If by "perfectly" you mean "have hard-to-predict somewhat nonlocal
behavior that makes any code relying on this a hard-to-read footgun",
then the answer might be "yes". For pretty much any other definition of
"perfectly", I'm fairly sure the answer is "no".
Great to hear those counter-examples as I don't know enough about ASI,
Still in the context of ASI, here are some examples of why ASI is a bad
idea:
1) What does this return?
function f() {
return
5;
}
2) What does this alert?
var str = "hello";
var x = str
[x].forEach(() => alert(x))
Now back to automatic comma insertion... In your example:
function doStuff(
x
y
z
){
}
if someone changes doStuff to take an array as the second arg and you
modify the call as:
function doStuff(
x
[y]
z
){
}
suddenly you need to insert a comma after the "x" to preserve the right
semantics, no? This is not terribly intuitive or obvious. It gets even
worse in a situation like this:
function doStuff(
x
/* The next argument is an array for good reasons that we
will now expound on in a long comment, etc, etc */
[y]
){
}
Quick, tell me without testing this or looking at the spec for a while
whether this is a valid call to doStuff, with one argument, or a syntax
error that would trigger comma insertion.
But more generally, if you just use your favorite search engine on the
phrase "automatic semicolon insertion", you will get a slew of articles
explaining the pitfalls.
-Boris
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