How to restructure an array of strings based on prefix

#How to restructure an array of strings based on prefix?

Source: StackOverflow

Question

I have an array containing a list of filenames:

    var files = ['home_01.ai','home_02.ai','home_03.ai','imprint_01.ai','imprint_02.ai']

What I want to do is reorganise this array into a multi-dimensional array that groups together each file with the same prefix. In this case:

    var firstArray = ['home_01.ai','home_02.ai','home_03.ai'], /*home*/
    secondArray = ['imprint_01.ai','imprint_02.ai']; /*imprint*/

How could I achieve that when there can be a variable amount of prefixes that can be any length in my file array?

Answer

You can do it with AlaSQL JavaScript data processing library.

Here is the solution for your problem:

    var res = alasql('COLUMN OF SELECT ARRAY(_) FROM ? \
         GROUP BY _->split("_")->0',[files]);

This statement returns array of arrays grouped by prefix:

    [ [ 'home_01.ai', 'home_02.ai', 'home_03.ai' ],
      [ 'imprint_01.ai', 'imprint_02.ai' ] ]

Here:

• COLUMN OF - return only first column of query
• SELECT ... FROM ? GROUP BY ... - select statement
• ARRAY(_) - group records in array
• FROM ? - query from parameter [files]
• GROUP BY ->split("")->0 - take a value, split it with '' and then take first element of array (similar to JS r.split('')[0]