获取javascript中值最高的数组key

Question

I have a array like

arr[1] = 234;
arr[2] = 345;
...

arr[40] = 126;

How can I get the index of the element with the highest value without reiterating the array?

Answer 1

You can apply Math.max and pass the array as its arguments-

arr.indexOf(Math.max.apply(window,arr))

But now Math.max is doing the iterating, just as sort would do.

Somebody has to look at each item in an unsorted array...

Answer 2

With jQuery, is as simple as:

// Get the max value from the array    
maxValue = Math.max.apply(this, arr);

// Get the index of the max value, through the built in function inArray
$.inArray(maxValue,arr);

Answer 3

Get the array key with the highest value in javascript

var cars = ["Saab", "Volvo", "BMW"];
var max_car_result = cars[cars.length-1];
alert(max_car_result);

Answer 4

If the array is not ordered you cannot do this without iterating.

Answer 5

Try this:

var max_index = -1;
var max_value = Number.MIN_VALUE;
for(var i = 0; i < arr.length; i++)
{
    if(arr[i] > max_value)
    {
        max_value = arr[i];
        max_index = i;
    }
}

Answer 6

You could use a function to set the variable. And keep track of the max in that function. Here's a quick example without type checking, testing, or support for removing a value.

Array.prototype.maxValue = null;

Array.prototype.setIndex = function(index, value){
  this[index] = value;
  if (value > this.maxValue || this.maxValue == null)
    this.maxValue = value;
}


var arr = new Array();
arr.setIndex(0, 234);
arr.setIndex(1, 500);
arr.setIndex(2, -5);

var maxValue = arr.maxValue;

Obviously this is nicer if you're currently setting items like this:

var arr = new Array();
arr[0] = 1;
arr[1] = 500;
arr[2] = 2;

Rather than this:

var arr = { 1, 500, 2 };

The downside is its not natural and requires you to use function to get the correct results.

Answer 7

Keep the array sorted or use a heap.

Otherwise iterate. Even if you found some trick to do it it would still require iterating underneath so why not iterate?

If it seems like too much code, put it in a separate routine.

Answer 8

Is old question but here is an my simple emulation of PHP script max() made in javascript:

function max(array){
    if(Object.prototype.toString.call( array ) === '[object Array]'){
        return array[(array.length-1)];
    }
    else return 0;
}

This return value of last key in array or 0 if nothing found.

Maby someone helps.

You can use it like:

var array = ['bananaman','spiderman','ironman','superman','batman','manman'];
var getLast = max(array);
if(getLast !== 0)
    alert(getLast); // manman

Answer 9

Two solution: to sort descending order and get the first element or:

function bigger(array) {
  if (array.length < 1) {
    return -1;
  }
  bigger = 0;
  for(var i=1; i<array.length;i++ ) { 
    if(array[i] > array[bigger]) {
      bigger = i;
    }
  }
  return bigger;
}

you cold optimize using two variables, one for the position and other for the content.

Answer 10

Either you will have iteration somewhere (in your code or in JQuery.each()) or you can define something like this:

Array.prototype.mpush = function(v)
{
  var maxv = this.maxValue || Number.MIN_VALUE;
  if( v > maxv ) { this.maxValue = v; this.maxIndex = this.length; }
  this.push(v);
}

and use that arr.mpush(v) to populate your array. In this case the array will have maxIndex property.