CoffeeScript按键对对象进行排序

Question

I'm trying to pick up some CoffeeScript but stuck on sorting an array of objects by key. Here's what I tried:

sortByKey = (array, key) ->
    array.sort( (a,b) -> a[key] < b[key] ? -1 : a[key] > b[key] ? 1 : 0 )

testarr = [{i: 5, b:7}, {i:9, b:15}, {i:-4, b:-99}]
sortByKey(testarr, 'i')
val = el['b'] for el in testarr
alert val

My alert shows only -99, whereas I would have expected to see -99, 7, 15. What am I doing wrong?

Answer 1

There is no ternary operator in CoffeeScript. Examine your compiled JavaScript and you would be able to see this immediately.

You need to drop your nested ternary operators (which is a bad practice even in a language that supports them) and use an if / else :

sortByKey = (array, key) ->
  array.sort (a,b) ->
    if a[key] < b[key]
      -1
    else if a[key] > b[key]
      1
    else
      0

Next, your array comprehension is wrong. You've done this:

a = b for b in c

That's identical to

for b in c
  a = b

Each element is assigned in turn to a , and only the final b is left in a after the loop completes.

If you want to assign the result of the comprehension itself to a variable, you need parenthesis:

a = (b for b in c)

Or, in your case

val = (el['b'] for el in testarr)