Javascript and regex: split string and keep the separator

Question

I have a string:

var string = \"aaaaaa
† bbbb
‡ cccc\"

And I would like to split this string w

Answer 1

I've been using this:

String.prototype.splitBy = function (delimiter) {
  var 
    delimiterPATTERN = '(' + delimiter + ')', 
    delimiterRE = new RegExp(delimiterPATTERN, 'g');

  return this.split(delimiterRE).reduce((chunks, item) => {
    if (item.match(delimiterRE)){
      chunks.push(item)
    } else {
      chunks[chunks.length - 1] += item
    };
    return chunks
  }, [])
}

Except that you shouldn't mess with String.prototype, so here's a function version:

var splitBy = function (text, delimiter) {
  var 
    delimiterPATTERN = '(' + delimiter + ')', 
    delimiterRE = new RegExp(delimiterPATTERN, 'g');

  return text.split(delimiterRE).reduce(function(chunks, item){
    if (item.match(delimiterRE)){
      chunks.push(item)
    } else {
      chunks[chunks.length - 1] += item
    };
    return chunks
  }, [])
}

So you could do:

var haystack = "aaaaaa
† bbbb
‡ cccc"
var needle =  '
&#?[a-zA-Z0-9]+;';
var result = splitBy(haystack , needle)
console.log( JSON.stringify( result, null, 2) )

And you'll end up with:

[
  "
† bbbb",
  "
‡ cccc"
]