交集

mix.js

function mix(arrays) {
  if (arguments.length < 1) return [];

  var allElems = [];
  var repeatRegStr = [];

  for (var i = 0, len = arguments.length; i < len; ++i) {
    if (i === 0) {
      repeatRegStr.push('(-?(?!0\\d)\\d+(?:\\.\\d+|)(?:[eE][+-]?\\d+|))');
    } else {
      repeatRegStr.push('\\1');
    }
    allElems = allElems.concat(arguments[i]);
  }

  allElems.sort(function(a, b) {
    return a - b;
  });

  var allElemsStr = allElems.join(':') + ':';
  var repeatReg = new RegExp(repeatRegStr.join(':') + ':', 'g');

  var matchResult = allElemsStr.match(repeatReg);

  return matchResult.map(function(e, i, a) {
    return parseFloat(e);
  });
}

console.log(mix([1, 2, 3, 4, 5, 6, 7, 8], [1, 3, 5, 7, 9], [1, 4, 7]));