Since each Dart script runs in a new isolate, with its own global state, it is not really helpful (or meaningful) to run Dart code one statement at a time, from the console. There is, in principle, no way of adding code to a running isolate. Unless we introduced new semantics for compiling new lines and adding them to a script, all of the effects of a single Dart statement would be confined to the new isolate running that line (and the DOM state).. The least intrusive way to add code to an existing isolate in the debugger would, I suppose, be to add a new top-level function, and then call that function. But I doubt this is that useful.

I think most of the use case for running Dart code at the console is med by tools that would allow objects to be inspected and changed, and would let you step through an existing script, and let you get to the code you want to test using breakpoints and watchpoints.

It isn't clear if you are referring to dev tools running the javascript code, that was produced by the dart comipler, or to dev tools running on dartium, so I'm not sure what aread this belongs in.

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This comment was originally written by antonm@google.com

Added this to the Later milestone.

This comment was originally written by @bgourlie

wheese's response makes it apparent why this is not trivially implemented, but I think it's vastly important to accommodate this considering it is something that can be done in javascript, and it would be taking a step back if I were unable to do so.

For my particular use case, I just want to call methods on globally defined objects within a particular isolate -- I don't want to redefine them or add new code. Of course, I don't know if this makes the solution any more trivial, or is universally useful enough to implement in this limited fashion.

This comment was originally written by antonm@google.com

Set owner to podivilov@google.com.

This comment was originally written by dbro...@gmail.com

I am new to Dart so let me know if I am mistaken here, but it seems to me that simply being able to interact with the DOM through the console would be immensely helpful. I don’t need to be able to interact with running code (other than indirectly).

This comment was originally written by dbrockman...@gmail.com

Hmm, perhaps I misunderstood what was said earlier about isolates. I guess you are saying that I wouldn’t for example be able to define a variable on one line in the console, and then use that variable on the next line?

Set owner to @jacob314.

This should be implemented with Jacob's CL:

https://codereview.chromium.org/23710032/

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This is fixed as of Dart release 0.8.1.2 .

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This comment was originally written by bangkok...@gmail.com

as of download from 2013/11/19, do not think it works

String s1 = 'hello'
SyntaxError: Unexpected identifier

if included file has nothing but
   String s1 = 'hello';

s1
ReferenceError: s1 is not defined

Make sure the context of the console is set to Dart not the JS context.
On the status bar of the console you will see a drop down where the top entry is <javascript page context>
Click on that list and select one of the Dart libraries loaded into your program.
As another tip, when defining new variables in the console, only use "var" instead of specifying types. Specifying a type for a console variable is unsupported and will generate an error.

You can verify that Dart code is running by writing the following two separate lines in the console:
var s1 = 'hello ${"dart"}'
s1

You should see
"hello dart"
in the console if you are running dart
but "hello ${"dart"}"
if you are running JavaScript.

This comment was originally written by bangko...@gmail.com

very good info. this would be most useful in
https://www.dartlang.org/tools/dartium/

This comment was originally written by bangko...@gmail.com

two issues:

1. when the page is refreshed the context is always reset to <javascript
   page context>.
2. if actually using dart sources, .../$script is a far more useful default

This comment was originally written by bangko...@gmail.com

cannot declare a class from the console

==> "'': Error: line 2 pos 1: unexpected token 'class'

is there some special syntax here, like having to declare variables with
var &tc?

Sorry defining classes from the console is not supported at this time.
You can however define arbitrarily complex closures from the console.
e.g.

var bar = (foo) { print("Hello $foo"); return ()=> 42;}