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Asked: 2026-05-27T19:09:01+00:00

I’ve got a bunch of numbers in an array and I need to do

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I’ve got a bunch of numbers in an array and I need to do some statistics on them. I need to know how many of each number there are in the array.

Here’s the array: 

myArray =
[2, 3, 3, 3, 4, 4, 5, 5, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 14, 14, 14, 14, 14, 14, 15, 15, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 20, 20, 20, 20, 20, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23, 24, 24, 24, 25, 25, 25, 25, 25, 25, 25, 25, 25, 26, 26, 27, 27, 28, 30, 30, 31, 31, 31, 31, 31, 31, 31, 31, 32, 32, 32, 32, 32, 32, 32, 33, 33, 33, 33, 33, 33, 34, 34, 35, 35, 35, 35, 35, 35, 36, 36, 36, 36, 36, 36, 37, 37, 37, 37, 37, 37, 37, 38, 38, 38, 38, 38, 39, 39, 39, 39, 39, 39, 40, 40, 40, 41, 41, 42, 42, 42, 42, 42, 42, 43, 43, 43, 44, 44, 44, 44, 44, 45, 45, 46, 46, 46, 46, 46, 46, 46, 47, 47, 47, 47, 47, 47, 48, 48, 48, 49, 49, 49, 49, 49, 49, 49, 49, 49, 50, 50, 50, 50, 50, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 52, 52, 53, 53, 53, 53, 53, 53, 53, 54, 54, 54, 55, 55, 55, 55, 55, 56, 57, 57, 57, 57, 57, 57, 57, 58, 59, 59, 59, 59, 59, 60, 60, 60, 60, 60, 61, 61, 62, 62, 63, 63, 63, 64, 64, 64, 64, 64, 65, 65, 66, 66, 66, 67, 67, 67, 68, 68, 68, 69, 69, 69, 69, 69, 69, 70, 70, 71, 71, 71, 71, 71, 71, 71, 72, 73, 73, 73, 73, 74, 74, 74, 75, 75, 75, 76, 77, 78, 78, 79, 79, 80, 80, 81, 81, 81, 81, 81, 82, 82, 82, 82, 83, 83, 83, 83, 84, 84, 84, 85, 85, 85, 85, 85, 86, 86, 86, 86, 86, 86, 87, 87, 87, 88, 88, 89, 89, 90, 90, 91, 91, 91, 92, 93, 94, 95, 95, 95, 95, 95, 96, 96, 96, 96, 97, 97, 99, 99, 99, 99, 99, 101, 101, 102, 102, 103, 103, 105, 105, 105, 106, 107, 107, 108, 108, 109, 109, 109, 109, 110, 112, 112, 113, 113, 113, 114, 114, 115, 116, 116, 117, 118, 120, 121, 121, 121, 122, 122, 123, 123, 123, 124, 124, 124, 124, 125, 126, 127, 128, 129, 130, 130, 131, 131, 131, 131, 132, 133, 133, 134, 134, 134, 136, 136, 136, 136, 137, 137, 137, 138, 138, 138, 139, 139, 139, 140, 141, 141, 142, 142, 143, 144, 144, 144, 144, 145, 150, 150, 153, 155, 159, 160, 160, 161, 162, 164, 164, 166, 176, 180, 180, 180, 181, 181, 187, 191, 192, 193, 194, 197, 200, 203, 211, 216, 224, 251, 280, 333]

Here’s what I’m using to parse through it currently (which is not working very well): 

    for (var key in myArray){
        var obj = myArray[key];

        var count = 0;
        while(obj < 30){
            myArrayStats[0] = count;
            obj++;
        }
        while(obj > 30 && obj < 40){
            myArrayStats[1] = count;
            obj++;
        }
        //etc....
    }

Creating a new array using object literals would be much nicer and easier to use, but I’m not sure how to do it.

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1 Answer

  1. Editorial Team

    This just works whether your array is sorted or not, but it shouldn’t be much slower than any algorithm that takes advantage of the fact that it is sorted anyways:

    var myArrayStats = [];
for(var i = myArray.length; i--;)
    myArrayStats[myArray[i]] = (myArrayStats[myArray[i]] || 0) + 1;

console.log(myArrayStats[6]);  // Outputs 7
console.log(myArrayStats[10]); // Outputs 5
console.log(myArrayStats[20]); // Outputs 5

    If you want to do this for only a portion of the original array than use slice() to get the portion of the array you want and then do the same thing as above on that array:

    var mySubArray = myArray.slice(0,30);
var myArrayStats = [];
for(var i = mySubArray.length; i--;)
    myArrayStats[mySubArray[i]] = (myArrayStats[mySubArray[i]] || 0) + 1;

console.log(myArrayStats[6]);  // Outputs 7
console.log(myArrayStats[9]);  // Outputs 7
console.log(myArrayStats[10]); // Outputs undefined
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