Redeclaration with let statement won't raise error

[meetwudi]

In the Let declarations part, you mentioned that if I declared a variable with var and then redeclare it with let, it will raise error. But actually it doesn't. I ran the following code in latest v8 (harmony mode), which turned out to be just fine.

> var test = 1;
> let test = 1;

What will actually raise the error is declaring two variables with same name with let in the same scope. For example:

> let test = 1;
> let test = 2;
SyntaxError: Variable 'test' has already been declared
    at Object.exports.createScript (vm.js:44:10)
    at REPLServer.defaultEval (repl.js:118:23)
    at bound (domain.js:255:14)
    at REPLServer.runBound [as eval] (domain.js:268:12)
    at REPLServer.<anonymous> (repl.js:277:12)
    at REPLServer.EventEmitter.emit (events.js:104:17)
    at REPLServer.Interface._onLine (readline.js:202:10)
    at REPLServer.Interface._line (readline.js:531:8)
    at REPLServer.Interface._ttyWrite (readline.js:806:14)
    at ReadStream.onkeypress (readline.js:101:10)

[getify]

These engines are not up to spec. The condition you state is an error condition, regardless of v8 not being compliant yet.

[meetwudi]

Thanks!

[yoshuawuyts]

Wasn't let removed from the spec some time ago? Remember seeing a talk by @getify about it.

[rwaldron]

@yoshuawuyts let is still in the spec

[getify]

I know what @yoshuawuyts is probably talking about.

I mention in my "New Rules For JS" talk (as well as my "YDKJS: Scope & Closures" book) that the let (x = ..) { .. } (aka "let statement") form of let was not added to the ES6 spec, which is true. However, the let x = .. (aka "let declaration") form of let _WAS_ added to the ES6 spec.

As far as I can tell, @nzakas is only covering the standardized "let declaration" form in his book, so everything he's said is accurate.

[nzakas]

That is correct.​ I'm covering what should work based on the current state of the spec.