String permutation from Java to Javascript

Question

I am new to Javascript and I was trying to reproduce a Java string permutation using Javascript but I cannot get the correct result.

Note: I followed this algorithm here (Hemant's answer): String permutation with recursion

Here is my code:

function getAllPermutations(input){
  var permutations = [];

  function loop(prefix, input){

      var len = input.length;

      if(len==0) {
          permutations.push(prefix);
       }
      else{
      for(i = 0; i < len; i++){
        loop(prefix + input.charAt(i),input.substr(0,i) + input.substr(i+1,len));
       }
      }
     }

  loop("", input);

  return permutations;
}

When I call getAllPermutations("good"), it's only returning ["good"]. What's going on with this code? Am I missing anything about the call back scope?

Jireugi · Accepted Answer · 2016-09-18 05:23:01Z

0

The problem is that the variable i in the for loop is defined globally. Therefore in each recursion the variable retains the value of the former iteration.
It can be fixed by writing var in front of the variable to make it a local variable like in the following code snippet.

for(var i = 0; i < len; i++){
// ...
}

answered Sep 18, 2016 at 5:23

Jireugi

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