JavaScript数组的5种迭代方法

  var arr = [1,2,3,4,5];
  //every() filter() some() forEach() map()
  var res = arr.every(function(i,index,o){
    return i>2;
  });
  console.log(arr); //[1,2,3,4,5]
  console.log(res); //false

  var some = arr.some(function (i, k, l) {
    return i>2;
  });
  console.log(arr);//[1,2,3,4,5]
  console.log(some);//true

  var filter = arr.filter(function (i, k, l) {
    return i>2;
  });
  console.log(arr);//[1,2,3,4,5]
  console.log(filter);//[3,4,5]

  var forEach = arr.forEach(function (i, k, l) {
    return i>2;
  });
  console.log(arr);//[1,2,3,4,5]
  console.log(forEach);//undefined

  var map = arr.map(function (i, k, l) {
    return i>2;
  });
  console.log(arr);//[1,2,3,4,5]
  console.log(map);//[false,false,true,true,true]