JavaScript: Iterate over an array with custom start and end points

Question

JavaScript: Iterate over an array with custom start and end points

I have a massive collection of items — approximately 30000 in total.

     startIndex = Math.floor( Math.random() * arr.length )

I am interested in selecting a random subset from the entire collection.

My goal is to iterate through the array starting at startIndex and ending at startIndex + n.

Important note: It is crucial for this array to remain unchanged, as it would be too resource-intensive to re-render the entire dataset.

What approach would be most effective for this task? Should I use a for loop or a while loop?

javascript arrays loops

Answer 1

Answer №1

Instead of initializing var i = 0 at the beginning of your for loop, consider setting it to the starting point and modify the condition from i < array.length to i < ending_index.

This adjustment allows you to iterate through all indexes between the specified start and end_index, replicating the behavior of a traditional for loop that typically starts from 0 and goes until the end of the array.

Answer 2

Instead of initializing var i = 0 at the beginning of your for loop, consider setting it to the starting point and modify the condition from i < array.length to i < ending_index.

This adjustment allows you to iterate through all indexes between the specified start and end_index, replicating the behavior of a traditional for loop that typically starts from 0 and goes until the end of the array.

Answer 3

Answer №2

If you want to handle a large array in batches, give this method a try. You may need to adjust the batch size depending on your needs.

function ProcessLargeArrayInBatches() {
    var largeArray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36];

    var batchSize = 10;

    for (var start = 0; start < largeArray.length; start = start + batchSize) {
        ProcessBatch(largeArray, start, GetEndIndex(start, batchSize, largeArray.length));
    }

}

function GetEndIndex(startIndex, batchSize, arrayLength) {
    var endIndex = startIndex + batchSize;

    if (endIndex > arrayLength) {
       return arrayLength;
    }

    return endIndex;
}

function ProcessBatch(someArr, startIndex, endIndex) {
    console.log("Start Batch from " + startIndex + " to " + endIndex);
    for (var i = startIndex; i < endIndex; i++) {
       console.log(someArr[i]);
    }
    console.log("Ending Batch from " + startIndex + " to " + endIndex);
}

Answer 4

If you want to handle a large array in batches, give this method a try. You may need to adjust the batch size depending on your needs.

function ProcessLargeArrayInBatches() {
    var largeArray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36];

    var batchSize = 10;

    for (var start = 0; start < largeArray.length; start = start + batchSize) {
        ProcessBatch(largeArray, start, GetEndIndex(start, batchSize, largeArray.length));
    }

}

function GetEndIndex(startIndex, batchSize, arrayLength) {
    var endIndex = startIndex + batchSize;

    if (endIndex > arrayLength) {
       return arrayLength;
    }

    return endIndex;
}

function ProcessBatch(someArr, startIndex, endIndex) {
    console.log("Start Batch from " + startIndex + " to " + endIndex);
    for (var i = startIndex; i < endIndex; i++) {
       console.log(someArr[i]);
    }
    console.log("Ending Batch from " + startIndex + " to " + endIndex);
}

Answer 5

Answer №3

let numbers = [5, 6, 7, 8];
let groupSize = 3;
let startingPoint = Math.floor(Math.random() * (numbers.length - groupSize));

for (let j = startingPoint; j < startingPoint + groupSize; j++) {
    // Your custom code goes here
}

Answer 6

let numbers = [5, 6, 7, 8];
let groupSize = 3;
let startingPoint = Math.floor(Math.random() * (numbers.length - groupSize));

for (let j = startingPoint; j < startingPoint + groupSize; j++) {
    // Your custom code goes here
}

JavaScript: Iterate over an array with custom start and end points

Answer №1

Answer №2

Answer №3

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