Is there an idiomatic way to test array equality in Coffeescript?

Question

The expression

[1, 2, 3] == [1, 2, 3] 

evaluates to false in Coffeescript but is there a concise, idiomatic way to test array equality?

Answer 1

If you are dealing with arrays of numbers, and you know that there are no nulls or undefined values in your arrays, you can compare them as strings:

a = [1, 2, 3] b = [1, 2, 3]  console.log "#{a}" is "#{b}" # true console.log '' + a is '' + b # true 

Notice, however, that this will break as soon as you start comparing arrays of other things that are not numbers:

a = [1, 2, 3] b = ['1,2', 3]  console.log "#{a}" is "#{b}" # true 

If you want a more robust solution, you can use Array#every:

arrayEqual = (a, b) ->   a.length is b.length and a.every (elem, i) -> elem is b[i]  console.log arrayEqual [1, 2, 3], [1, 2, 3]   # true console.log arrayEqual [1, 2, 3], [1, 2, '3'] # false console.log arrayEqual [1, 2, 3], ['1,2', 3]  # false 

Notice that it's first comparing the lengths of the arrays so that arrayEqual [1], [1, 2, 3] doesn't return true.