CODEWITHSUNDEEP
javascriptnode.js
Anthony Encarnacion
Anthony Encarnacion

Reputation: 13

Filter function giving me error with strings Javascript

Implement the function unique_in_order which takes as argument a sequence and returns a list of items without any elements with the same value next to each other and preserving the original order of elements.

For example:

uniqueInOrder('AAAABBBCCDAABBB') == ['A', 'B', 'C', 'D', 'A', 'B']

uniqueInOrder('ABBCcAD') == ['A', 'B', 'C', 'c', 'A', 'D']

uniqueInOrder([1,2,2,3,3]) == [1,2,3]

I tried solving this problem using a filter function on the given parameter. Here is my attempt:

var uniqueInOrder = function (iterable) { 
return iterable.filter(function(current, index, array){
    if (index === 0){
      return true;
    }
    else if (current[current.length - 1] === array[index]){
      return false;
    } 
    else {
      return true;
    }
  });
};

The issue is that I get this error and I don't understand why it doesn't detect filter as a function.

Here is the parameter I give it:

uniqueInOrder("AAAABBBCCDAABBB");

Here is the error:

const newArray = iterable.filter(function (current, index, array) {
                            ^

TypeError: iterable.filter is not a function
    at uniqueInOrder (c:\Users\Anthony\source\repos\Web Dev\Unique in Order\script.js:2:29)
    at Object.<anonymous> (c:\Users\Anthony\source\repos\Web Dev\Unique in Order\script.js:15:1)
    at Module._compile (internal/modules/cjs/loader.js:1133:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1153:10)
    at Module.load (internal/modules/cjs/loader.js:977:32)
    at Function.Module._load (internal/modules/cjs/loader.js:877:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:74:12)
    at internal/main/run_main_module.js:18:47

Upvotes: 1

Views: 197

Answers (2)

Sebastian B.
Sebastian B.

Reputation: 2201

Strings are not arrays (opposed to some other languages), so they don't provide a filter method:

Either convert the given iterable parameter to an array with iterable = Array.from(iterable) (Array.from is not natively supported by IE) or explicitly split strings with if (typeof iterable === 'string') { iterable = iterable.split(''); }

Upvotes: 0

Jack Bashford
Jack Bashford

Reputation: 44125

Strings don't have filter - plus, it's a lot simpler to make a Set then convert to an array:

var uniqueInOrder = iterable => [...new Set(iterable)];

Or to keep with your idea (ignoring your algorithm and simply fixing the error), do a simple ES6 spread:

return [...iterable].filter(...);

Or if it's an old environment:

return (typeof iterable == "string" ? iterable.split("") : iterable).filter(...);

Upvotes: 1

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