JavaScript: refactoring, avoiding array.push()

Question

I've got a function in an object like this:

arrayofElements: function(item) {

    var result = [];

    if (item.isA) {
        result.push(new Div('aClass', labels['A']));
    }

    if (item.isC) {
        result.push(new Div('cClass', labels['C']));
    }

    if (item.isD) {
        result.push(new Div('dClass', labels['D']));
    }

    return result;
},

How can this be refactored? I dislike having to push() each item conditionally.

Answer 1

arrayofElements: function(item) {

var result = [],
    items = ['A', 'C', 'D'];
while(var i=0; i < items.length; i++) {
  if(item["is" + items[i]]) {
    result.push(new Div(items[i] + 'Class', labels[items[i]]))
  }
}
return result;
},

Remember that obj.foo is the same as obj['foo'] in Javascript

Answer 2

You could move the is* properties to a sub-object so as to isolate them, and loop over the sub-object's properties

item.is={A:'aClass', C:'cClass'};
...
arrayofElements: function(item) {
    var result = [];
    for (p in item.is) {
        result.push(new Div(item.is[p], labels[p]));
    }
    return result;
},

The values in item.is could be the classes (as shown), or the values in item.is could be objects with a class property, or you could use the property name p as an index in another object to get the classes. Which depends largely on what the items represent and what the element classes are most closely associated with.

Answer 3

A variant of Larry's solution:

arrayofElements: function(item) {
  var result = [], letters = ['A','C','D'], ltr, i, len;
  len = letters.length;
  for (i = 0; i < len; i++) {
    ltr = letters[i];
    if (item["is"+ltr]) {
      result.push(new Div(ltr.toLowerCase()+"Class", labels[ltr]));
    }
  }
  return result;
},

Answer 4

This function avoids using push() and is functionally identical to yours:

arrayofElements: function(item) {

    if (item.isA) {
       return [new Div('aClass', labels['A'])];
    }

    if (item.isC) {
       return [new Div('cClass', labels['C'])];
    }

    if (item.isD) {
       return [new Div('dClass', labels['D'])];
    }

    return [];
},