CoffeeScript / JavaScript中的变量作用域

Question

In the following code, I want to use the markers variable, which I expect to be an array of objects (eg, [{...},{...},{...}] ). However depending on the indentation level, the variable shows an empy array (ie, [] ).

jQuery ->
  markers = []
  $.getJSON '/users.json', (data) ->
    for obj in data
      marker = {}
      marker =
        lastname: namify(obj.name)
        address: obj.address
      markers.push(marker)
    console.log("3rd level", markers) # It shows the array I want.
  console.log("2nd level", markers)   # "markers" shows an empty array.

My Expectation - populated array in the 2nd level. Result - an empty array in the 2nd level.

How can I retrive the array as shown in the 3rd level when I'm at the 2nd level.

Answer 1

You are populating your array inside the callback function. So it's populated after you print the result. Problem is not about scope, it is about order of execution.

If you make a synchronous request you should see what you expect:

jQuery ->
  markers = []
  $.ajax
    url: '/users.json'
    dataType: 'json'
    async: false
    success: (data) ->
      for obj in data
        marker = {}
        marker =
          lastname: namify(obj.name)
          address: obj.address
        markers.push(marker)
    console.log("3rd level", markers)
  console.log("2nd level", markers)