Create strings using .reduce() in Javascript

Question

I need to be able to take a list of strings, and come up with a list of all possible combinations of those strings combined.

["asdf", "ghj","ew","ptum"]

It should get a list something like this, up to n

["agep", "aget", "ageu", ... "fjwm"]

What would I do to get these?

what `agep` come from? Your example does not make sense to me! — T D Nguyen, Jan 29 '16 at 07:11
N! Problem. loop 1-to-N-1, loop 2-to-N,combine,end-loop,end-loop. — Mark Manning, Jan 29 '16 at 07:11
@NguyenDoanTung `agep`, `a` from the first string, `g` from the second string, etc. — Derek 朕會功夫, Jan 29 '16 at 07:12

score 0 · Answer 1 · answered Jan 29 '16 at 07:17

You can create an array of letters from the list of strings , like in your case -> list of strings :

list = ["asdf", "ghj","ew","ptum"]

array of letters would be :-

arr = ["a","s",...,"m"]

then iterate through the array, for each letter make combination with other letters in array ...

the logic will be like this...

//for strings of length 3 ..
for(i in arr){
   for(j in arr){
      for(k in arr){
          if(i!=j && j!=k)
              result=i+j+k
                   }
                }
             }

p.s I am not into JS , I just told one logic to do this , you can now implent the logic in your language.

Goblinlord · Accepted Answer · 2016-01-29T08:07:00.057

0

What you are asking is relatively trivial... some for loops can do this fairly easily. Below is one such method you could use.

var input = ["asdf", "ghj", "ew", "ptum"];

function combinations(r, n) {
  var o = [];
  if (r.constructor.name === "String")
    r = r.split("");
  if (n.constructor.name === "String")
    n = n.split("");

  r.forEach(function(i) {
    n.forEach(function(j) {
      o.push(i + j);
    })
  })
  return o;
}

document.write("<pre>"+JSON.stringify(input.reduce(combinations),null,2)+"</pre>");

edited Jan 29 '16 at 08:07

answered Jan 29 '16 at 08:01

Goblinlord

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WOAH!!!! Thank you! I never even knew about reduce... :( I learn something new every day. This will come in handy later. Thanks again. – Corbbin Goldsmith Jan 29 '16 at 19:35
While this is good, it doesn't work for less than 2 strings. Like if I have string `"io"` it should get both i & o, but it doesn't. I'm just going to pass each of the characters when the length of the strings is 1 and not do the reduce. – Corbbin Goldsmith Jan 30 '16 at 08:43
not sure why you would want to use it with a single string as you can just do "io".split("") and you have your list. You could easily filter for that but in the context you gave it didn't make much sense to make it that way – Goblinlord Jan 30 '16 at 10:14

Create strings using .reduce() in Javascript

2 Answers2