CODEWITHSUNDEEP
javascriptarraysindexing
Prakhar Gyawali
Prakhar Gyawali

Reputation: 555

getting new nth indexed number of element from an array according to the given nth element in a circular manner

so the problem is simple . here i want to return the new nth element of an array according to the previous nth element sent by the user.for example

['1','3','5','7','9','11']

if a user sends a value of 3 then I would like to return 7, if the user sends 5 then I would like to return 9 , if they send 7 then 11 and when they send 11 then I want to return 3. basically its like puting the array in a circular mode and return the next element.

here is my code.

var indices=['1','3','5','7','9','11'];
var index_to_add=2;
var uservalue='1';/// will be sent by the user
var index=indices.indexOf(uservalue);            
return indices[index+index_to_add];

everything here works fine but when the array finishes or nears the end then I get undefined instead of element from the first. how can i get the element from the beginning if the element index is undefined or the array finishes?

Upvotes: 0

Views: 59

Answers (2)

Andrew Corrigan
Andrew Corrigan

Reputation: 1057

If I've interpreted your question correctly, a solution would be to encapsulate the processing within a recursive function, if you're after readable code and are unfamiliar with the Modulo function (doing it this way also makes it easier to change the process in the future):

const indices=['1','3','5','7','9','11'];
var index_to_add=2;
var uservalue='1';/// will be sent by the user
console.log(GetElemAtIndex(GetIndex(userValue) + index_to_add));


function GetIndex(userValue) {
    return indices.indexOf(userValue); // If this is -1 the user has entered something not in the array
}

function GetElemAtIndex(toFind) {
    if (indices.length > toFind) {
        return indices[toFind];
    }
    else {
        return GetElemAtIndex(toFind - indices.toLength);
    }
}

The modulo function in Taxel's answer is a more efficient way of doing the GetElemAtIndex block.

Upvotes: 1

Taxel
Taxel

Reputation: 4207

Using the Modulo operator:

return indices[(index+index_to_add) % indices.length];

Note: this will only handle the case when uservalue is actually part of the array. You might want to add a clause like if(index === -1) return 'Uservalue not in array.' or throw an error.

Upvotes: 3

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