w3shcool里对于 slice() 方法的描述貌似不对

Question

http://www.w3school.com.cn/jsref/jsref_slice_array.aspend 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3console.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