Javascript /咖啡脚本附加TypeError：不是函数

Question

Why isn't working?

It works if I change variable msg for a string value.

Code:

console.log full_messages # Array [ "text to be displayed" ]
for msg in full_messages
  $('#error_explanation ul').append('<li>'+ msg +'</li>')

Error message:

TypeError: msg is not a function

Answer 1

Your problem is in your whitespace (or lack thereof):

'<li>'+ msg +'</li>'

CoffeeScript thinks that the second + in that is a unary operator so the whole thing is interpreted as:

'<li>' + msg(+'</li>')

If you put spaces on both sides of your binary operators:

'<li>' + msg + '</li>'
#     ^^^   ^^^

then CoffeeScript does what you're expecting it to. Rule of Thumb : always put spaces on both sides of binary operators.

You could also use string interpolation:

"<li>#{msg}</li>"

That becomes exactly the same JavaScript as '<li>' + msg + '</li>' but is (arguably) more readable and idiomatic.