Sorting Arrays (Javascript)

Question

i'm trying to construct a code that uses the selection-sort method, but i'm having trouble. When i press my button nothing happens. I figure having a second pair of eyes on the code would help me find out what's wrong.

Is my swap() function correct? Is my select() function correct? What am I doing wrong? All help is welcome!

<input id="input1" type="number" min="5" max="1000" onchange="first(); sortButton();">

<p id="demo"></p>

<!-- button appears here, once a value is entered into the input field -->
<p id="buttons1" onclick="select();"></p>


<p id="demo2"></p>

<script>


// once input1 value changes this outputs a random value less than N (value of input1) N times, then dumps out the random numbers in id="demo"

var arr = [];
function first() {
var N = document.getElementById("input1").value;
while(arr.length < N)

{var randomnumber = Math.ceil(Math.random()*N);
arr[arr.length] = randomnumber;}
document.getElementById("demo").innerHTML = arr;}


// Once input1 value changes, this buttons appears in id="buttons"
function sortButton() {document.getElementById("buttons1").innerHTML =
'<button type="button" onclick="select();">Select Sort</button>';}


function swap(arr, i, min) {
var temp = arr[i];
arr[i] = arr[min];
arr[min] = temp;}


// meant to sort (selection sort method) the random numbers in id="demo" once the button is clicked

function select() {var len = arr.length, min, i,  j;
for (i = 0; i < len; i++){min = i; for (j = i+1; j < len; j++){if (arr[j] < arr[min]){min = j;}} if (i != min){swap(arr, i, min);} } return arr;}




</script>

Inner Html is expected to be a string. Convert arr to string using arr.join("") — Jonas Wilms
– Jonas Wilms, Commented Nov 13, 2016 at 18:51
where would i write that? -- bare with me i'm very new to js lol — anon
– anon, Commented Nov 13, 2016 at 18:53
document.getElementById("demo2").innerHTML = arr.join("");} correct? — anon
– anon, Commented Nov 13, 2016 at 18:57

Jonas Wilms · Accepted Answer · 2016-11-13 19:11:37Z

2

Your select function is a mess. Theres a standard function called sort, that does that for you:

function select(){
arr.sort(function(a,b){
 //if a<b keep it, if not swap
 if(a<b){
   return 0;
 }else{
   return 1;
 }
 });

https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Array/sort

You can even short it:

function select(){
 arr.sort((a,b)=>a-b);
 }

(See arrow functions for more info)

edited Nov 13, 2016 at 19:11

answered Nov 13, 2016 at 19:03

Jonas Wilms

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