Top counting loop for value within an array

Question

In this example, how to get a list or an array of the largest 3 values by an ‎hierarchic ordering (1. 306, 2. 267, 3. 263)?

var array = [267, 306, 108, 263, 67];
var largest = Math.max.apply(Math, array); // 306

Possible duplicate http://stackoverflow.com/questions/1063007/how-to-sort-an-array-of-integers-correctly — Ataur Rahman Munna, May 15 '17 at 10:47

score 4 · Accepted Answer · answered May 15 '17 at 10:30

4

You need to sort largest to smallest then slice the top three items.

var arr = [267, 306, 108, 263, 67];

console.log(arr.sort((a, b) => b - a).slice(0, 3));

.as-console-wrapper { top: 0; max-height: 100% !important; }

answered May 15 '17 at 10:30

Mr. Polywhirl

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Thanks. Works fine. But the values refer to a string and I don´t know how to refer it to the value after sorting. I´ve added it behind the value (using +'string') but it´s not usefully by sorting. Any solution? – user3236072 May 15 '17 at 12:37
Yeah, use: `(a, b) => b.localeCompare(a)` or `parseInt(b, 10) - parseInt(a, 10)`. – Mr. Polywhirl May 15 '17 at 13:02
Great! :) Thank you. – user3236072 May 16 '17 at 06:31

Marcin Pevik · Answer 2 · 2017-05-15T10:40:18.960

0

You might use Array.sort() and Array.slice() methods to get what you want.

var array = [267, 306, 108, 263, 67];
var sorted = array.sort(function(a,b) { return b - a }); // sort the array in descending order
var largest = sorted.slice(0, 3); // get first three array elements
console.log(largest); // Array [ 306, 267, 263 ]

edited May 15 '17 at 10:40

answered May 15 '17 at 10:31

Marcin Pevik

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Your answer should be precise and usable. If you give some instruction [not the exact answer], then use comment, not put it in as a answer. – Ataur Rahman Munna May 15 '17 at 10:32
Thanks for the hint – Marcin Pevik May 15 '17 at 10:38
Welcome. But your answer is identical to @Mr. polywhril. Identical answer should be marked as duplicate and should be removed. – Ataur Rahman Munna May 15 '17 at 10:40
You're very well informed. But it's not my call anyway. – Marcin Pevik May 15 '17 at 10:43

score 0 · Answer 3 · answered May 15 '17 at 10:48

You can get it like:

var array = [267, 306, 108, 263, 67];

findLargest3();

function findLargest3(){ 
    // sort descending
    array.sort(function(a,b){
        if(a < b){ return 1; } 
        else if(a == b) { return 0; } 
        else { return -1; }
    });
    alert(array.slice(0, 3));

}

Working Js Fiddle

score 0 · Answer 4 · answered May 15 '17 at 11:42

You can write a helper function, like this:

function getTopItems(arr, howMany, comparator) {
    if (typeof comparator !== "function") {
        comparator = function(a, b) {return a > b;};
    }
    function addToOutput(item) {
        var previous = item;
        var found = false;
        for (var innerIndex = 0; innerIndex < output.length; innerIndex++) {
            if (found) {
                var aux = previous;
                previous = output[innerIndex];
                output[innerIndex] = aux;
            } else if (comparator(item, output[innerIndex])) {
                found = true;
                var aux = previous;
                previous = output[innerIndex];
                output[innerIndex] = aux;
            }
            console.log(output);
        }
        if (output.length < howMany) output.push(previous);
    }
    var index = 0;
    var output = [];
    while (index < arr.length) {
        addToOutput(arr[index++]);
    }
    return output;
}

Top counting loop for value within an array

4 Answers4