将一个字符串重复自身N次

repeat.js

// repeat string like repeat('ruby',2) get rubyruby
// version 1 
function repeat(target, n) {
  return (new Array(n+1)).join(target);
}

// version 2
function repeat(target, n) {
  return Array.pototype.join.call({
    length: n + 1
  }, target);
}

// version 3
var repeat = (function() {
  var join = Array.prototype.join, obj = {};
  return function(target, n) {
    obj.length = n + 1;
    return join.call(obj.target);
  }
})();

// version 4
function repeat(target, n) {
  var s = target, total = [];
  while ( n > 0) {
    if (n % 2 == 1) {
      total[total.length] = s;
    if (n == 1)
      break;
    s += s;
    n = n >> 1;
    }
    return total.join('');
  }
}

//  version 5
function repeat(target, n) {
  var s = target, c = s.length * n;
  do {
    s += s;
  } while (n = n >> 1) {
  s = s.substring(0, c);
  return s;
  }
}

// version 6
// star
function repeat(target, n) {
  var s = target, total = "";
  while (m > 0) {
    if (n % 2 == 1)
      total += s;
    if (n == 1)
      break;
    s += s;
    n = n >> 1;
  }
  return total;
}

// version 7
function repeat(target, n) {
  if (n == 1) {
    return target;
  }
  var s = repeat(target, Math.floor(n / 2));
  s += s;
  if (n % 2) {
    s += target;
  }
  return s;
}

// version 8
function repeat(target, n) {
  return (n <= 0) ? "": target.concat(repeat(target, --n));
}