How can I regex this array/string?

Question

array = ['item1', 'item2', 'item3', 'item4']
output = array.toString()

This gets me "item1,item2,item3,item4" but I need to turn this into "item1, item2, item3, and item4" with spaces and "and"

How could I construct a regex process to do this rather then substringing and find/replacing?

Is this the best way?

Thanks!

Answer 1

Try this:

var array = ['item1', 'item2', 'item3', 'item4'];
array.push('and ' + array.pop());
var output = array.join(', ');
// output = 'item1, item2, item3, and item4'

---

Edit: if you really do want a regex-based solution:

var output = array.join(',')
 .replace(/([^,]+),/g, '1,ドル ').replace(/, ([^,]+)$/, ' and 1ドル');

---

Another edit:

Here's another non-regex approach that doesn't mess with the original array variable:

var output = array.slice(0,-1).concat('and ' + array.slice(-1)).join(', ');

• HBP: But it does change the array which might cause problems downstream. Also does not quite work for arrays of length 1.
• jmar777: I guess if that's a problem you can just do array2 = array.slice()
• jmar777: Good point though - I should have mentioned that my approach isn't side-effect free.
• jmar777: Added two alternative approaches - one with regular expressions, and another one that does array manip, but leaves array intact.

Answer 2

This version handles all the variations I could think of :

function makeList (a) {
 if (a.length < 2)
 return a[0] || '';
 if (a.length === 2)
 return a[0] + ' and ' + a[1];
 return a.slice (0, -1).join (', ') + ', and ' + a.slice (-1);
} 
console.log ([makeList ([]), 
 makeList (['One']), 
 makeList (['One', 'Two']), 
 makeList(['One', 'Two', 'Three']),
 makeList(['One', 'Two', 'Three', 'Four'])]);
// Displays : ["", "One", "One and Two", "One, Two, and Three", "One, Two, Three, and Four"]

Answer 3

var output = array.join(", ");
output = outsput.substr(0, output.lastIndexOf(", ") + " and " + output.substr(output.lastIndexOf(" and "));