How to compare strings in an array: Javascript

Question

I have an array which looks like

var arr = ["a|c", "a|e", "x|z"];
for(var x in arr){
    var appsplit = x.split("|");
}

If the first value(ex: a) in the elements matches then it should combine the values

Ex: output ace xz

Please advice how this approach can be done.

Answer 1

You are testing everyone's reading comprehension with that riddle.

var pairs = {};

var arr = ["a|c", "a|e", "x|z"];
for(var x in arr)
{
    var appsplit = arr[x].split("|");
    if(pairs[appsplit[0]] !== "undefined")
    {
        pairs[appsplit[0]] = pairs[appsplit[0]] + appsplit[1];
    }
    else
    {
        pairs[appsplit[0]] = appsplit[1];
    }

}

var matches = [];

for(var x in pairs)
{
    matches.push(x + pairs[x]);
}

console.log(matches);

We need to map out the arr elements in this object called pairs. The first value in your split would be the key and the second value is appended (or assigned if it's the first match to the key)

You made an error of splitting x, but you are only splitting the index of the element, not the actual value of the element. arr[x] is the actual value, where x specifies the index in the array.

After we've gone through your arr, we can now merge the key with the values. Your output is contained in matches where the key in each pair is prepended to the value of the key's pair.

Answer 2

Some simple code that would to the trick here.

var arr = ["a|c", "a|e", "x|z", "c|b", "z|e", "c|a"];
var resultObj = {};
arr.forEach(function(element, index){
     var array = element.split('|');
     if(array.length!==2){
        console.log("skipping, invalid input data", element);
     } else {
        var firstLetter = array[0];
        var secondLetter = array[1];
        if(resultObj[firstLetter]){
           resultObj[firstLetter].push(secondLetter);
        } else {
            resultObj[firstLetter]=[secondLetter];
        }
     }

});

Object.keys(resultObj).forEach(function(key){
    console.log(key + "," + resultObj[key]);
});

Answer 3

You can use .reduce(), Set to not accumulate duplicate values, .some() to check if previous array contains value in current array, .map(), Array.from() and .join() to convert array to string

var arr = ["a|c", "a|e", "x|z"];
var res = arr.reduce(function(a, b) {
  var curr = b.split("|");
  var set = new Set;
  for (let prop of curr) set.add(prop);
  if (!a.length) {
    a.push(set)
  } else {
    for (prop of a) {
      if (curr.some(function(el) {
          return prop.has(el)
        })) {
        for (el of curr) {
          prop.add(el)
        }
      } else {
        for (let prop of curr) set.add(prop);
        a.push(set)
      }
    }
  }
  return a
}, []).map(function(m) {
  return Array.from([...m], function(el) {
    return el
  }).join("")
});

console.log(res);

Answer 4

I feel like this can be done more elegantly, but I didn't have time to streamline it. :) The below code will do what you want, though:

var aStartArray = **ARRAY_VALUE_HERE**;
var aSplitResultStrings = [];

// step through each element in the array
for (var i = 0, iSALength = aStartArray.length; i < iSALength; i++) {

    // split the values for the current array element
    var aSplitVal = aStartArray[i].split("|");
    var bStringDoesNotExist = true;

    // loop through the "result strings" array
    for (var j = 0, iSRSLength = aSplitResultStrings.length; j < iSRSLength; j++) {

        // if the first letter from the array element = the first letter of the current "result string" . . .
        if (aSplitResultStrings[j].charAt(0) === aSplitVal[0]) {

            // append the second letter of the array value to the current result string
            aSplitResultStrings[j] = aSplitResultStrings[j] + aSplitVal[1];

            // indicate that a match has been found and exit the "result string" loop
            bStringDoesNotExist = false;
            break;
        }
    }

    // if there are no result strings that start with the first letter of the array value . . .
    if (bStringDoesNotExist) {

        // concatenate the two values in the current array value and add them as a new "result string"
        aSplitResultStrings.push(aSplitVal[0] + aSplitVal[1]);
    }
}

Using these arrays, the results are:

aStartArray = ["a|c", "a|e", "x|z"] //results in:
aSplitResultStrings = ["ace", "xz"]

aStartArray = ["a|b", "a|c", "a|d", "a|e", "x|y", "x|z"] //results in:
aSplitResultStrings = ["abcde", "xyz"]

aStartArray = ["a|b", "d|e", "d|f", "x|y", "g|h", "g|i", "m|n", "g|j", "a|c", "x|z"] //results in:
aSplitResultStrings = ["abc", "def", "xyz", "ghij", "mn"]

As I said, this could be more elegant (for example, you could probably use Map to make iterating through the "result strings" easier), but this makes the steps pretty clear and should get you going down the right path towards a final solution.