Preventing duplicate index values in JavaScript loop iterations

Question

Preventing duplicate index values in JavaScript loop iterations

I have a specific scenario in JavaScript where I need to traverse an array and check if the index matches any predefined options. If it does, I either push or print the option once. Here is the array:

["ITEM1", "dummyData1", "dummyData2", "ITEM2", "dummyData1", "dummyData2", "ITEM3", "dummyData1", "dummyData2", "ITEM4", "dummyData1", "dummyData2", "ITEM4", "dummyData1", "dummyData2", "ITEM4", "dummyData1", "dummyData2", "ITEM4", "dummyData1", "dummyData2", "ITEM5", "dummyData1", "dummyData2", "ITEM5", "dummyData1", "dummyData2", "ITEM6", "dummyData1", "dummyData2", "ITEM7", "dummyData1", "dummyData2", "ITEM7", "dummyData1", "dummyData2"]

To achieve this, I aim to loop through the array for every THING, and if the current THING index matches the previous one, I skip it; otherwise, I add it to the array. Although I initially tried using global variables, they did not provide the desired solution.

Expected Output:

[ITEM1 ..... ITEM7]




 var currentItem ;
var myArr;
for (var j = 1; j <= 100; j++) {

 for (var i = 0; i <= res[j].length-1; i++) {

 var option1 = (res[j][i].match(/THING1-/));
 var option2 = (res[j][i].match(/THING2-/));
 var option3 = (res[j][i].match(/THING3-/));
 var option4 = (res[j][i].match(/THING4-/));
 var item;
                            if (option1 != null)
                               item = "THE_THING-1";
                            else    if (option2 != null)
                                 item = "THE_THING-2";
                            else       if (option3 != null)
                                item= "THE_THING-3";
                            else           if (option4 != null)
                                 item = "THE_THING-4";
if (currentItem!= item)
{
currentItem = item;
myArr.push("THING"+j)
}
}
}

javascript arrays

Answer 1

Answer №1

To discover all items in the array arr that are of the form ITEMc, where c is a constant, we can utilize a simple method involving a placeholder array:

var findUniqueItems = function (arr) {
    // placeholder array
    var p = [];
    
    for (var i = 0; i < arr.length; i++) {
        if (arr[i].slice(0,4) == "ITEM")
            p[i] = true;
    }
    
    return p.filter(function (d) { return d; }).map(function (d, i) { return i; });
}

This approach has an efficient time complexity of O(n) and requires only additional space of O(n). An alternative solution that involves looping through the array to check for duplicates would have a significantly slower time complexity of O(n^2).

Answer 2

To discover all items in the array arr that are of the form ITEMc, where c is a constant, we can utilize a simple method involving a placeholder array:

var findUniqueItems = function (arr) {
    // placeholder array
    var p = [];
    
    for (var i = 0; i < arr.length; i++) {
        if (arr[i].slice(0,4) == "ITEM")
            p[i] = true;
    }
    
    return p.filter(function (d) { return d; }).map(function (d, i) { return i; });
}

This approach has an efficient time complexity of O(n) and requires only additional space of O(n). An alternative solution that involves looping through the array to check for duplicates would have a significantly slower time complexity of O(n^2).

Answer 3

Answer №2

Are you looking to achieve the following task:

let itemList = [],
  dataArray = ['sampledata1', 'sampledata2'],
  itemNameBase = "ITEM";


for(let index = 1; index < 8; index++) {
   let currentName = itemNameBase + index;
   // Adjust data for individual items based on their names
   if(itemList.indexOf(currentName) == -1) {
      itemList.push(currentName);
      itemList = itemList.concat(dataArray);
   }
}

console.log(itemList);

Answer 4

Are you looking to achieve the following task:

let itemList = [],
  dataArray = ['sampledata1', 'sampledata2'],
  itemNameBase = "ITEM";


for(let index = 1; index < 8; index++) {
   let currentName = itemNameBase + index;
   // Adjust data for individual items based on their names
   if(itemList.indexOf(currentName) == -1) {
      itemList.push(currentName);
      itemList = itemList.concat(dataArray);
   }
}

console.log(itemList);

Answer 5

Answer №3

Give this a shot:

// To make the regex case insensitive, add "i" at the end
// Example: /^ITEM\d+$/i
var regex = /^ITEM\d+/;

var uniqueItems = {};
filteredArray = myArr.filter(function(element) {
    if(regex.test(element) && !uniqueItems.hasOwnProperty(element)) { 
        uniqueItems[element] = true;
        return true;
    }
    return false;
});

If you need to support older versions of Internet Explorer, remember that the filter function is only available from IE9 onward.

For an elegant solution for finding unique values in an array, visit Unique values in an array.

Answer 6

Give this a shot:

// To make the regex case insensitive, add "i" at the end
// Example: /^ITEM\d+$/i
var regex = /^ITEM\d+/;

var uniqueItems = {};
filteredArray = myArr.filter(function(element) {
    if(regex.test(element) && !uniqueItems.hasOwnProperty(element)) { 
        uniqueItems[element] = true;
        return true;
    }
    return false;
});

If you need to support older versions of Internet Explorer, remember that the filter function is only available from IE9 onward.

For an elegant solution for finding unique values in an array, visit Unique values in an array.

Preventing duplicate index values in JavaScript loop iterations

Answer №1

Answer №2

Answer №3

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