w3shcool里对于 slice() 方法的描述貌似不对

http://www.w3school.com.cn/jsref/jsref_slice_array.asp

end 可选。规定从何处结束选取。该参数是数组片断结束处的数组下标。

var arr = new Array(6)
arr[0] = "George"
arr[1] = "John"
arr[2] = "Thomas"
arr[3] = "James"
arr[4] = "Adrew"
arr[5] = "Martin"

console.log(arr) 
    //["George", "John", "Thomas", "James", "Adrew", "Martin"] 
console.log(arr.slice(2,4))
    //["Thomas", "James"]  James是第四个，但下标是3
console.log(arr)
    //["George", "John", "Thomas", "James", "Adrew", "Martin"] 

当然，还有一种理解就是 2 <= x < 4
不知道我的理解对不对，还是钻牛角了