Compared with the splice method, the slice method does not modify the original array.
1. Grammar and description
Description : Make a shallow copyof the original array through start and end(extract the array elements indexed from start to end)
Syntax :Array.slice([start[, end])
Parameters :
start : start index
end : end index
Return value : return a new array
Whether to change the original array : No
2. Parameters
1. No parameters
Description : Extract the array elements from the starting index (0) until the end
Return value : all array elements from the start index to the end index
Original array : no change
example
var arr = ['A', 'B', 'C', 'D'];
var res = arr.slice()
console.log('arr', arr);
// ['A', 'B', 'C', 'D']
console.log('res', res);
// ['A', 'B', 'C', 'D']
2. There is only one parameter start
Description : Extract the array elements from the start index until the end
Negative number : means to extract array elements from the reciprocal start index
Positive number : extract array elements from the start index until the end
Return value : all array elements from the start index to the end index, if the start is greater than the original array length, an empty array is returned
Original array : no change
example
// 1. 正数
var arr = ['A', 'B', 'C', 'D'];
var res = arr.slice(1)
console.log('arr', arr);
// ['A', 'B', 'C', 'D']
console.log('res', res);
// ["B", "C", "D"]
// 2. 负数
var arr = ['A', 'B', 'C', 'D'];
var res = arr.slice(-1)
console.log('arr', arr);
// ['A', 'B', 'C', 'D']
console.log('res', res);
// ["D"]
// 3. 大于数组长度的值
var arr = ['A', 'B', 'C', 'D'];
var res = arr.slice(6)
console.log('arr', arr);
// ['A', 'B', 'C', 'D']
console.log('res', res);
// []3. There are two parameters start , end
Description : Extract array elements from the start index to the end index (including start, but not including end)
Return value : all array elements from start index to end index
Original array : no change
example
var arr = ['A', 'B', 'C', 'D'];
var res = arr.slice(1, 3)
console.log('arr', arr);
// ["A", "B", "C", "D"]
console.log('res', res);
// ["B", "C"]Three, pay attention
If only one parameter larger than the length of the array is passed in, an empty array is returned
No matter how the array elements are extracted, the original array remains unchanged