js内建函数

• Object.keys()
  var a = {a:1, b:2, c:3};
  var b = Object.keys(a); //["a", "b", "c"]
• Object.values()
  var a = {a:1, b:2, c:3};
  var b = Object.values(a); //[1, 2, 3]
• [].map()
  var a = [1, 2, 3, 4, 5, 6];
  var b = a.map(function (item) {
  return item + 10;
  }); //[11, 12, 13, 14, 15, 16]
• [].filter()
  var a = [1, 2, 3, 4, 5, 6];
  var b = a.filter(function (item) {
  if (item % 2 === 1) {
  return true;
  }
  }); // [1, 3, 5]