Coding clarity of closure for load event

问题

Is there are clear way to write this closure for the load event on line #4:

for i,item of m
  # add item once image loaded
  new_item = $("<img src='#{util.image_url(item, 'large')}' />")
  new_item.on 'load', ((item) => (=> @add_item(item)))(item)
  $("#preload-area").append(new_item)

回答1:

You want a do loop:

When using a JavaScript loop to generate functions, it's common to insert a closure wrapper in order to ensure that loop variables are closed over, and all the generated functions don't just share the final values. CoffeeScript provides the do keyword, which immediately invokes a passed function, forwarding any arguments.

Something like this:

for i, item of m
  do (item) =>
    new_item = $("<img src='#{util.image_url(item, 'large')}' />")
    new_item.on 'load', => @add_item(item)
    $("#preload-area").append(new_item)        

来源：https://stackoverflow.com/questions/20057967/coding-clarity-of-closure-for-load-event