finding substrings within arrays - javascript

Question

I need to find the substrings within arrays. If I have an array: ["abc", "abcd", "abcde", "xyz"], the method should return me the array members: "abc", "abcd", "abcde" as each is a substring or a superstring of the other, but it should exclude "xyz". What is the best possible method in javascript.

Answer 1

Use Array#filter

var arr = ["abc", "abcd", "abcde", "xyz"];

console.log(arr.filter(function(el) {
  return el.indexOf('abc') > -1;
}));

Edit: Use Array#some if you want to make filter based of some values in the array with respect to current element!

var arr = ["abc", "abcd", "abcde", "xyz"];

console.log(arr.filter(function(el, index) {
  return arr.some(function(e, i) {
    if (i !== index) {
      return e.indexOf(el) > -1 || el.indexOf(e) > -1;
    }
    return false;
  })
}));

Answer 2

You can simply use 2 nested loops, but the complexity is O(n^2)

function find_substrings(arr) {
    var res = [];
    for (var i=0; i<arr.length; i++) {
        for (var j=0; j<arr.length; j++) {
            if (i !== j && (arr[i].indexOf(arr[j]) > -1 || arr[j].indexOf(arr[i]) > -1)) {
                res.push(arr[i]);
                break;
            }
        }
    }
    return res;
}
var arr = ["abc", "abcd", "abcde", "xyz"];
console.log(find_substrings(arr));
   

Answer 3

You could use some optimized loops with short cut and an object for the items.

var data = ["abc", "abcd", "42", "abcde", "422", "xyz", "q", "1q"],
    result = function (array) {
        var i, j,
            r = {};

        for (i = 0; i < array.length - 1; i++) {
            if (r[array[i]]) {
                continue;
            }
            for (j = i + 1; j < array.length; j++) {
                if (r[array[j]]) {
                    continue;
                }
                if (array[i].indexOf(array[j]) !== -1 || array[j].indexOf(array[i]) !== -1) {
                    r[array[i]] = true;
                    r[array[j]] = true;
                }
            }
        }
        return array.filter(function (a) { return r[a]; });
    }(data);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }