Split string in JavaScript using regex with zero width lookbehind

Question

I know JavaScript regular expressions have native lookaheads but not lookbehinds.

I want to split a string at points either beginning with any member of one set of characters or ending with any member of another set of characters.

Split before ເ, ແ, ໂ, ໃ, ໄ. Split after ະ.

In: ເລື້ອຍໆມະຫັດສະຈັນເອກອັກຄະລັດຖະທູດ

Out: ເລື້ອຍໆມະ ຫັດສະ ຈັນ ເອກອັກຄະ ລັດຖະ ທູດ

I can achieve the "split before" part using zero-width lookahead:

'ເລື້ອຍໆມະຫັດສະຈັນເອກອັກຄະລັດຖະທູດ'.split(/(?=[ໃໄໂເແ])/)

["ເລື້ອຍໆມະຫັດສະຈັນ", "ເອກອັກຄະລັດຖະທູດ"]

But I can't think of a general approach to simulating zero-width lookbehind

I'm splitting strings of arbitrary Unicode text so don't want to substitute in special markers in a first pass, since I can't guarantee the absence of any string from my input.

Answer 1

Instead of spliting, you may consider using the match() method.

var s = 'ເລື້ອຍໆມະຫັດສະຈັນເອກອັກຄະລັດຖະທູດ',
    r = s.match(/(?:(?!ະ).)+?(?:ະ|(?=[ໃໄໂເແ]|$))/g);

console.log(r); //=> [ 'ເລື້ອຍໆມະ', 'ຫັດສະ', 'ຈັນ', 'ເອກອັກຄະ', 'ລັດຖະ', 'ທູດ' ]