How do I convert a JavaScript forEach loop/function to CoffeeScript

Question

Background: I'm trying to convert some JavaScript code which uses the the Crossfilter library with D3.js data visualization library into CoffeeScript.

What is the best way to convert a JavaScript forEach loop/function into CoffeeScript?

Here's the JavaScript code:

// A little coercion, since the CSV is untyped. flights.forEach(function(d, i) {     d.index = i;     d.date = parseDate(d.date);     d.delay = +d.delay;     d.distance = +d.distance; }); 

Can CoffeeScript do an in-line function inside a loop? Right now I'm guess I need it broken out into a function and loop:

coerce = (d) ->      d.index    = 1      d.date     = parseDate(d.date)      d.delay    = +d.delay      d.distance = +d.distance  coerce(flights) for d in flights 

Answer 1

use a comprehension

for d, i in flights   console.log d, i 

The code above translates to

var d, i, _i, _len;  for (i = _i = 0, _len = flights.length; _i < _len; i = ++_i) {   d = flights[i];   console.log(d, i); } 

so you can see d and i are what you want them to be.

Go here and search for "forEach" for some examples.

Finally, look at the first comment for some more useful info.

Answer 2

The direct translation is:

flights.forEach (d, i) ->   d.index = i   d.date = parseDate(d.date)   d.delay = +d.delay   d.distance = +d.distance 

or you can use an idiomatic version:

for d,i in flights   d.index = i   d.date = parseDate(d.date)   d.delay = +d.delay   d.distance = +d.distance