Group array items based on variable javascript

Question

I have an array that is created dynamic from an xml document looking something like this:

myArray[0] = [1,The Melting Pot,A]
myArray[1] = [5,Mama's MexicanKitchen,C]
myArray[2] = [6,Wingdome,D]
myArray[3] = [7,Piroshky Piroshky,D]
myArray[4] = [4,Crab Pot,F]
myArray[5] = [2,Ipanema Grill,G]
myArray[6] = [0,Pan Africa Market,Z]

This array is created within a for loop and could contain whatever based on the xml document

What I need to accomplish is grouping the items from this array based on the letters so that all array objects that have the letter A in them get stored in another array as this

other['A'] = ['item 1', 'item 2', 'item 3'];
other['B'] = ['item 4', 'item 5'];
other['C'] = ['item 6'];

To clarify I need to sort out items based on variables from within the array, in this case the letters so that all array objects containing the letter A goes under the new array by letter

Thanks for any help!

Answer 1

You shouldn't use arrays with non-integer indexes. Your other variable should be a plain object rather than an array. (It does work with arrays, but it's not the best option.)

// assume myArray is already declared and populated as per the question

var other = {},
    letter,
    i;

for (i=0; i < myArray.length; i++) {
   letter = myArray[i][2];
   // if other doesn't already have a property for the current letter
   // create it and assign it to a new empty array
   if (!(letter in other))
      other[letter] = [];

   other[letter].push(myArray[i]);
}

Given an item in myArray [1,"The Melting Pot","A"], your example doesn't make it clear whether you want to store that whole thing in other or just the string field in the second array position - your example output only has strings but they don't match your strings in myArray. My code originally stored just the string part by saying other[letter].push(myArray[i][1]);, but some anonymous person has edited my post to change it to other[letter].push(myArray[i]); which stores all of [1,"The Melting Pot","A"]. Up to you to figure out what you want to do there, I've given you the basic code you need.

Answer 2

Try groupBy function offered by http://underscorejs.org/#groupBy

_.groupBy([1.3, 2.1, 2.4], function(num){ return Math.floor(num); });

Result => {1: [1.3], 2: [2.1, 2.4]}