js 过滤器

var ary = [0,1,2];
ary[10] = 10;
ary.filter(function(x) {
  return x === undefined;
});

// A. [undefined x 7]
// B. [0, 1, 2, 10]
// C. []
// D. [undefined]

答案是C。

例子

var ary = [0,1,2];
ary[10] = 10;
ary.filter(function(x) {
  return x === 2;
});
console.log(ary)  //2

例子

var ary = [0,1,2];
ary[10] = 10;
ary.filter(function(x) {
  return x === 10;
});
console.log(ary)  //10