var string = 'Split this, but not this'
var arr = string.split(' '),
result = arr.slice(0,1);
result.push(arr.slice(1).join(' '));
var arr = string.split(' '),
result = arr.splice(0,1);
result.push(arr.join(' '));
const split = string.split(' ', 1);
result = [split[0], string.substr(split[0].length + 1)];