permutation - Find all lowercase and uppercase combinations of a string in Javascript - Stack Overflow

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I am looking for this stackoverflow question to be answered in Javascript.

So if my input is "word", the function should return:

word, Word, wOrd, WOrd, woRd, WoRd, etc..

here's what i have so far but it only produces the permutations (doesn't capitalize anything)

var perm = function(str){
var results = [];

var bos = function(reference, appendTo){
 appendTo = appendTo || "";
 if(reference.length === 0) {
  results.push(appendTo);
 }
 for(var i = 0; i < reference.length; i++){
  var current = reference.splice(i, 1);
  bos(reference, appendTo+current);
   reference.splice(i, 0, current)
 }
} 
bos(str.split(""));
return results;
}
perm("word");

I am looking for this stackoverflow question to be answered in Javascript.

So if my input is "word", the function should return:

word, Word, wOrd, WOrd, woRd, WoRd, etc..

here's what i have so far but it only produces the permutations (doesn't capitalize anything)

var perm = function(str){
var results = [];

var bos = function(reference, appendTo){
 appendTo = appendTo || "";
 if(reference.length === 0) {
  results.push(appendTo);
 }
 for(var i = 0; i < reference.length; i++){
  var current = reference.splice(i, 1);
  bos(reference, appendTo+current);
   reference.splice(i, 0, current)
 }
} 
bos(str.split(""));
return results;
}
perm("word");

• javascript
• permutation
• uppercase
• lowercase

Share Improve this question Follow edited May 23, 2017 at 10:30 CommunityBot 111 silver badge asked Jan 16, 2015 at 20:22 user3068590user3068590 5911 silver badge55 bronze badges 6

• So where's your code? I can't see anything to ment on. – Mörre Commented Jan 16, 2015 at 20:23
• I'm going to go ahead and close this as a "work order." If this is a troubleshooting question, show us the work you have so far, and describe the difficulty you are having solving the problem. – Robert Harvey Commented Jan 16, 2015 at 20:24
• just like, you know, make a million randomy upper and lower case versions, then filter duplicates – dandavis Commented Jan 16, 2015 at 20:32
• 1 @dandavis: The actual solution is a bit more... focused than that. – Robert Harvey Commented Jan 16, 2015 at 20:32
• @RobertHarvey: my answer is as focused as this question is on the ways of SO... – dandavis Commented Jan 16, 2015 at 20:34

 |  Show 1 more ment

3 Answers 3

Sorted by: Reset to default 7

One option would be generating capitalization permutations via binary logic.

As a simple example of the snippet below, consider the following table where the left column is the binary representation of the current permutation and the right column is the resulting capitalization:

0000 | word
1000 | Word
0100 | wOrd
1100 | WOrd
...
1111 | WORD

// Used to display the results
const write = (msg) => {
  document.body.appendChild(document.createElement('div')).innerHTML = msg;
};

const input = "word";
const letters = input.split("");
const permCount = 1 << input.length;

for (let perm = 0; perm < permCount; perm++) {
  // Update the capitalization depending on the current permutation
  letters.reduce((perm, letter, i) => {
    letters[i] = (perm & 1) ? letter.toUpperCase() : letter.toLowerCase();
    return perm >> 1;
  }, perm);

  const result = letters.join("");
  write(result);
}

Note that theoretically this approach would work all the way up to Number.MAX_SAFE_INTEGER, up to inputs of length 52, but realistically you'll run into performance issues.

var s = "word";
var sp = s.split("");
for (var i = 0, l = 1 << s.length; i < l; i++) {
  for (var j = i, k = 0; j; j >>= 1, k++) {
    sp[k] = (j & 1) ? sp[k].toUpperCase() : sp[k].toLowerCase();
  }
  var st = sp.join("");
  var d = document.createElement("p");
  d.appendChild(document.createTextNode(st));
  document.body.appendChild(d);
}

With Nit's solution in mind, I wanted to offer a slightly refactored solution that may be easier to follow

  var perm = function(str){
    var results = [];
    var arr = str.split("");
    var len = Math.pow(arr.length, 2);

    for( var i = 0; i < len; i++ ){
      for( var k= 0, j = i; k < arr.length; k++, j >>=1){
        arr[k] = ( j & 1 ) ? arr[k].toUpperCase() : arr[k].toLowerCase();
      }
      var bo = arr.join("");
      results.push(bo);
    }
    return results;
  }

  perm("word");

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