Array.splice在Firefox控制台中不起作用

Question

Trying the following code from the MDN site

var myFish = ['angel', 'clown', 'mandarin', 'surgeon'];

// removes 0 elements from index 2, and inserts 'drum'
var removed = myFish.splice(2, 0, 'drum');

Doesn't assign to remove the expected output of splice ['angel', 'clown', 'drum', 'mandarin', 'surgeon'] , but instead and empty array [] .

Answer 1

I think you are confused by the return value of splice . It does not return the modified array, but the elements removed. In this case, you removed none, so if you log removed , you get an empty Array .

var myFish = ['angel', 'clown', 'mandarin', 'surgeon'];
var removed = myFish.splice(2, 0, 'drum');
console.log(myFish);
console.log(removed);

Output:

Array [ "angel", "clown", "drum", "mandarin", "surgeon" ]
Array [  ]

Answer 2

Array.prototype.splice在原始数组上运行。