[removed] Finding the most middle value in an arra

问题:

Closed. This question is off-topic. It is not currently accepting answers.

---

Want to improve this question? Update the question so it's on-topic for Stack Overflow.

Closed 5 years ago.

Okay, so what I need to do is return the most middle value in an array. And I'm supposed to use Math.round to calculate the middle index in the array. Just to be clear, I'm NOT talking about the median, just the middle value.

That's what I need to do in text, since I'm new at javascript I don't however know how to quite execute this. Any ideas?

Also, if you think,this question doesn't belong here or is stupid, please direct me to somewhere where I can find this information, I'm just trying to learn here.

function test(arr) {


}

回答1:

If you have an array with for example five items, the middle item is at index two:

var arr = [ item, item, middle, item, item];

Dividing the length by two and using Math.round would give you index three rather than two, so you would need to subtract one from the length first:

var middle = arr[Math.round((arr.length - 1) / 2)];

You say in your question that you are supposed to use Math.round, but if that is not a requirement, you can get the same result easier using Math.floor:

var middle = arr[Math.floor(arr.length / 2)];

For an array with an even number of items, that will give you the second of the two items that are in the middle. If you want the first instead, use Math.floor and substract one from the length. That still gives the same result for odd number of items:

var middle = arr[Math.floor((arr.length - 1) / 2)];

回答2:

Get the index in the middle of the Array:

var arr = [0, 0, 1, 0, 0];
var theMiddle = Math.floor(arr.length / 2); // index 2
var value = arr[theMiddle]; // value 1

One-liner:

var value = arr[arr.length / 2 | 0];

回答3:

You can try this one too:

function test(arr){      
  var middle_index = parseInt((arr.length/2).toFixed(), 10) - 1;
  if(middle_index === -1)
    alert('Array empty');
  else
    alert('Middle value in array ['+arr+'] is '+arr[middle_index]);
}

DEMO Link