Meteor variable scope

Question

I am fairly new to JavaScript and even newer to Meteor and am a little confused with what I think I know about variable scope and what the reality is. So I have this Meteor events helper:

Template.test.events({
  'click .selector': function (e) {
   e.preventDefault();
   var someArray = [1,2,3,4];
   var someVariable = "jquery slector data";

   console.log(someVariable); //this works as expected

   someArray.each(function(index, el) {
     console.log(someVariable); //not defined?
   })
  }
})

I was under the impression that any variables declared outside my .each function would be available inside of it? However I am getting not defined. Is this a Meteor specific thing or JavaScript in general? Also, how would I make the variables accessible inside the .each function without making them global? I don't think defining my variable inside the .each loop would be ideal because that would mean multiple trips to the DOM.

Thanks.

Answer 1

The problem seems to be that you're trying to use an each() method, which does not exist on Array.prototype. I believe you're looking for Array.prototype.forEach(). Underscore's _.each(array, callback) method would also work, and is more compatible with older browsers.

This should work:

Template.test.events({
  'click .selector': function (e) {
    e.preventDefault();
    var someArray = [1,2,3,4];
    var someVariable = "jquery slector data";

    console.log(someVariable);

    someArray.forEach(function(val, index) {
      console.log(someVariable);
    });
  }
});

Or, for compatibility:

   _.each(someArray, function(val, index) {
     console.log(someVariable);
   })

I believe your confusion stems from using jQuery's $.each() method, which works differently from the native forEach and Underscore's _.each(). For one, jQuery has a different argument order (notice that I switched the order of the arguments in the code). In general, I'd recommend using Underscore for collection-related functions and use jQuery primarily for DOM manipulation.