Trying to get all possible combinations using javascript

Question

i'm currently stuck on this problem,

suppose there is an array arr4(length is not fixed). I need to find all combinations of its element.

expected output is:

4-16D-5d 
4-16D-5e
4A-16D-5d
4A-16D-5e
4B-16D-5d
4B-16D-5e
4-15D-5d
4-15D-5e
4A-15D-5d
4A-15D-5e
4B-15D-5d
4B-15D-5e

What i tried is:

arr4=[['4','4A','4B'],['16D','15D'],['5d','5e']]; //may contains more elements
alert("arr4 "+arr4);
for(var k=0;k<arr4.length;k++){
 alert("k "+k);
 arr_v=arr4[k]
 alert("arrv"+arr_v);
 alert ("arrv lengt"+arr_v.length);
 for(var z=0;z<arr_v.length;z++){
 m=1;
 while(m<arr4.length){
 var test=arr4[m];
 for(var n=0;n<test.length;n++)
 alert(arr_v[z]+"<TEST>"+test[n]);
 }
 m++;
 }
} 

I kind of found a solution:

function product() {
 return Array.prototype.reduce.call(arguments, function(as, bs) {
 return [a.concat(b) for each (a in as) for each (b in bs)]
 }, [[]]);
}

BUT

arr4=[['4','4A','4B'],['16D','15D'],['5d','5e']];
alert(product(['4','4A','4B'],['16D','15D'],['5d','5e']);

The above works but the following don't work:

arr4=[['4','4A','4B'],['16D','15D'],['5d','5e']];
alert(product(arr4);

Anyone please suggest a solution

edit:solution here

• mtyson: thanks for that formatting, Kolink

Answer 1

You can compute the cartesian product of each sub-array. See this question and its answer

I tried it out, and since it goes off the length of each array, it should work no matter how many elements are in each list and return you a list of each product.

• j.b: It seems to work but why: arr4=[['4','4A','4B'],['16D','15D'],['5d','5e']]; alert(product(arr4); Don't work but alert(product(['4','4A','4B'],['16D','15D'],['5d','5e']); works. Any suggestions? thanks
• Charlie G: I'm assuming it doesn't take an array of arrays, rather it takes a "list" of arrays.
• j.b: thanks got the answer! stackoverflow.com/questions/9385755/…

Answer 2

var arr4 = [['4','4A','4B'],['16D','15D'],['5d','5e']];
for(var a = 0; a < arr4[1].length; a++){
 if(a != 0){
 document.write('<br /><br />');
 }
 for(var b = 0; b < arr4[0].length; b++){
 for(var c = 0; c < arr4[2].length; c++){
 document.write(arr4[0][b] + '-' + arr4[1][a] + '-' + arr4[2][c] + '<br />')
 }
 }
}

Obviously you don't want to use document.write but inside the last for loop is where each lines output will be using

arr4[0][b] + '-' + arr4[1][a] + '-' + arr4[2][b]

jsFiddle for those interested http://jsfiddle.net/5AmMU/1/

• j.b: Thanks a lot for your solution it works as expected. but this is where i'm stuck. the arr4 is not a fixed array. It gets poulated with random generated data. On different initialisations it may be as follows [['4','4A','4B'],['16D','15D'],['5d','5e'],['6d','8d'],['9g','9h',['9i']]); or [['4','4A','4B'],['16D','15D'])].
• James Hay: Well that would be fine if you were writing 'a' for arr4[0], b for arr4[1], c for arr4[2]. But you want them written in a specific order, how are you going to know the order you want them written in when it is a dynamically filled array?