Javascript to Coffeescript conversion doesn't work - coffeescript

Question

I have the following function that works perfectly in Javascript
function graphite_get_data(target) {
return context.metric(function(start, stop, step, callback) {
var fetch_time = new Date().getTime();
if ((fetch_time-current_time) < 6000 && saved_data.length > 0) {
callback(null, graphite_parse(saved_data));
}
else {
// -------------- Begin Request New Data ------------------
d3.json(host + "/render?format=json"
+ "&target=" + encodeURIComponent(target)
+ "&from=" + graphite_format_date(start - 2 * step)
+ "&until=" + graphite_format_date(stop - 1000),
function(data) {
if (!data) return callback(new Error("unable to load data"));
current_time = fetch_time
saved_data = data;
callback(null, graphite_parse(data));
});
// -------------- End Request New Data --------------------
} // else
}); // return
}
When I try to convert this to coffeescript using http://js2coffee.org, it doesn't work and I'm not sure how to debug:
graphite_get_data = (target) ->
console.log(global_pod)
console.log("hi") #prints
context.metric (start, stop, step, callback) ->
console.log("hi") #doesn't print
fetch_time = new Date().getTime()
if (fetch_time - current_time) < 6000 and saved_data.length > 0
callback null, graphite_parse(saved_data) # will use global variable test_pod
else
# -------------- Begin Request New Data ------------------
d3.json host + "/render?format=json" + "&target=" + encodeURIComponent(target) + "&from=" + graphite_format_date(start - 2 * step) + "&until=" + graphite_format_date(stop - 1000), (data) ->
return callback(new Error("unable to load data")) unless data
current_time = fetch_time
saved_data = data
callback null, graphite_parse(data) #will use global variable test_pod
# -------------- End Request New Data --------------------
Can you advise me on how to debug coffee script?
EDIT: I checked the the javascript generated and saw this
graphite_get_data = function(target) {
var fetch_time;
console.log("hi");
context.metric(function(start, stop, step, callback) {});
fetch_time = new Date().getTime();
console.log("hi");
if ((fetch_time - current_time) < 6000 && saved_data.length > 0) {
callback(null, graphite_parse(saved_data));
return true;
}
else {
d3.json(host + "/render?format=json" + "&target=" + encodeURIComponent(target) + "&from=" + graphite_format_date(start - 2 * step) + "&until=" + graphite_format_date(stop - 1000), function(data) {
if (!data) {
return callback(new Error("unable to load data"));
} // end if
current_time = fetch_time;
saved_data = data;
callback(null, graphite_parse(data));
return true;
}); //end function(data)
return true;
} //end else
// missing });
};
graphite_format_date = function(time) {
return Math.floor(time / 1000);
};
return graphite_parse = function(data) {
var pod_data, pod_json_data;
pod_json_data = $.grep(data, function(e) { return e.target === test_pod; });
pod_data = pod_json_data[0]["datapoints"].slice(1).map(function(d) { return d[0]; });
return pod_data;
};
}
}); // what is this here?? it should be in missing
}).call(this);
and found the problem to be }); missing in one place and added in another wrong place
still working on how to fix it

Answer 1

Can you advise me on how to debug coffee script?
Sure: use sourcemaps in Chrome. Keep in mind that sometimes a step in Coffee is several steps in JS, so sometimes you'll see odd looking stepping behavior.
Regarding the conversion of your code, I think you may have copied or pasted something wrong, because it looks fine to me:
graphite_get_data = (target) ->
context.metric (start, stop, step, callback) ->
fetch_time = new Date().getTime()
if (fetch_time - current_time) < 6000 and saved_data.length > 0
callback null, graphite_parse(saved_data)
else
# -------------- Begin Request New Data ------------------
d3.json host + "/render?format=json" + "&target=" + encodeURIComponent(target) + "&from=" + graphite_format_date(start - 2 * step) + "&until=" + graphite_format_date(stop - 1000), (data) ->
return callback(new Error("unable to load data")) unless data
current_time = fetch_time
saved_data = data
callback null, graphite_parse(data)
I've found js2coffee to be pretty reliable.
The biggest problem with your code is here:
context.metric(function(start, stop, step, callback) {});
That line didn't come over right in your version, but was fine in my version. I'm not sure why, I suspect you're missing some indents in the coffee code. Indents in coffeescript are very important.
I'd also recommend trying CoffeeScript Enhanced in Chrome -- js2coffee is paying for that traffic and not getting anything for it.

Answer 2

Looks like there is an indentation problem at the start of the coffeescript.
This is what generates your 2nd javascript:
graphite_get_data = (target) ->
context.metric (start, stop, step, callback) ->
fetch_time = new Date().getTime()
My coffeescript starts:
graphite_get_data = (target) ->
context.metric( (start, stop, step, callback) ->
fetch_time = new Date().getTime()
if ...
else ...
)

Answer 3

Can you advise me on how to debug coffee script?
You can't. Debug the resulting JavaScript. CoffeeScript isn't run directly, it gets trans-compiled to JavaScript.