converting nonadjacent columns to proper/title case in Google Sheets

I found something online and it works for changing text to title case; however, it only works on adjacent columns and I need to apply this to multiple nonadjacent columns. I will paste in the script. If you can give a fix to being able to take care of letting the script run on multiple nonadjacent columns that I specify, that would be great. I found some stuff online that says it can do that, but it is not clear to me. Here is the script that works:

function onEdit() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheets()[0];
var range = sheet.getRange("A_range");
range.activate();
var values = range.getValues();
if (values.map) {
range.setValues(values.map(function(row) {
return row.map(titleCase);
}));
}    
else {
range.setValue(titleCase(values));
}
}

function titleCase(str) {
return str.toString().split(/\b/).map(function(word) {
return word ? word.charAt(0).toUpperCase() + word.slice(1).toLowerCase() :      '';
}).join('');
}

This was from other people on this concept: The stuff to make it run on other columns is this:

var range1=sheet.getRange("A1:A19").getValues();
var range2=sheet.getRange("C1:C19").getValues();
var range=[],i=-1;
while ( range1[++i] ) { 
range.push( [ range1[i][0], range2[i][0] ] );
}

where range will have content from both columns.

data = sheet.getRange("A1:C19").getValues();
for (i = 0; i < data[0].length; i++) {
// do something with data[0][i]  
// do something with data[2][i]
}

I am not sure how to implement these 2 other ideas listed above. If you could be really specific, like actually put something into the first script that lets it run on Col. A and Col. D,for example, it would be much better than generalities, as I am really really new to this and have spent an enormous amount of time trying to learn it/get a handle on it. Thanks!