有人可以解释以下javascript代码段吗？ （菜鸟）

Question

The code is part of a program which returns the largest number within an array. Could someone please explain the following? Thanks

  if (parseInt(nums[0]) < parseInt(nums[1])) { nums.splice(0,1); }
        else { nums.splice(1,1); }

Answer 1

The basic is understanding what .splice does ^MDN

So it will modify your array by removing an item depending on the passed params

array . splice (start[, deleteCount[, item1[, item2[, ...]]]])

 var nums = ["2", 4]; if (parseInt(nums[0]) < parseInt(nums[1])) { nums.splice(0,1); // At index 0 remove 1 item } else { nums.splice(1,1); // At index 1 remove 1 item } console.log( nums ) // Modified array 

PS:

• as you noticed, the code works only for Arrays of length 2; it only compares the 0 and 1 index: nums[0] nums[1]
• If your array is [1, 1] (same values) - nothing will happen.
• If your array is [1.9, 1] - [1] will be returned, since you're using parseInt
• It's good habit to use radix with parseInt(value, radix) like parseInt(nums[0], 10)

Answer 2

Since you wrote NOOB I think it's important to be clear.

The splice method deletes 0 or more items from an array at a specified index and inserts 0 or more items at that index.

The signature is someArray.splice(startNdx, deleteCount[, ...itemsToInsert])

In the code you posted, this part

nums.splice(0,1);

starts at index 0 and deletes 1 element from the array. In other words if the array was [5, 6, 7] it would become [6, 7]

nums.splice(1,1);

This part starts at index 1 and deletes 1 element from the array. In other words if the array was [5, 6, 7] it would become [5, 7] .

The parseInt parts convert strings to integers which suggests the array contains strings not numbers (or might optionally contain strings). Assuming the array does contain strings then without the parseInt part it would be comparing strings not numbers which is a different type of compare. Since you didn't show the contents of the array it's hard to know exactly what it's trying to do but for example

"00" < "0000"  

is true where as

parseInt("00") < parseInt("0000") 

is not true. Similarly

"000_bob" < "000_jill" is true

but

parseInt("000_bob") < parseInt("000_jill") 

is not true

So the code is checking if the first value is less than the second but it's comparing by integer instead of string.

Someone else claimed this was bad code but it's not bad code without knowing the context it which it is being used.