Search two arrays in a loop and identify variations with a unique approach

Question

Search two arrays in a loop and identify variations with a unique approach

Currently, I am facing a challenge that I need assistance with. I am working on an updater that retrieves an XML list of files from a CDN and compares it with an older list to identify any file differences. The objective is to determine which files are out of date and require re-downloading. Unfortunately, I have not been able to find a suitable solution for this issue.

In my current setup, I am using three arrays: Array1, Array2, and DiffArray. Array1 contains the XML entries from the CDN, which can be considered as the master list. Array2 stores the old entries of the files we currently possess, acting as the slave list. Array3 is utilized to store the differences between the two arrays.

Here is a glimpse of the information present in each array. Each new line represents a separate index in the corresponding array:

Array1:

cbt/ar/816.mp3
2019-06-05T16:40:33.212Z
cbt/ar/817.mp3
2019-06-05T16:40:31.509Z
cbt/ar/818.mp3
2019-04-05T16:40:30.978Z
cbt/ar/819.mp3
2019-04-05T16:40:29.807Z

Array2:

cbt/ar/816.mp3
2019-04-05T16:40:33.212Z
cbt/ar/817.mp3
2019-04-05T16:40:31.509Z
cbt/ar/818.mp3
2019-04-05T16:40:30.978Z
cbt/ar/819.mp3
2019-04-05T16:40:29.807Z

A couple of points to note: 1.) This list consists of file names along with their last modified dates. 2.) Array1 includes newer versions of 816.mp3 and 817.mp3 files.

The goal is to compare the file versions, identify the discrepancies, and proceed to download the updated files.

The current code snippet I am using is as follows, but it does not effectively address the issue:

var a = [];
      for (var x = 0; x < remoteArray.length; x++) {
        a[remoteArray[x]] = true;
      }

      for (var y = 0; y < localArray.length; y++) {
        if (a[localArray[y]]) {
          delete a[localArray[y]];
        } else {
          a[localArray[y]] = true;
        }
      }

      for (var z in a) {
        diffArray.push(z);
        log.info("::DIFFERENCES::" + z);
      }

This code snippet only displays the literal differences and does not provide a clear indication of which files require updating.

javascript arrays loops

Answer 1

Answer №1

To simplify the process, consider converting your data into a list of objects that represent each file. While this may not be the most efficient method, it will enhance clarity and ease of maintenance.

function convertToListOfFiles(array) {
    var filesList = [];
    for (var i = 0; i < array.length; i += 2) {
        filesList.push({
            name: array[i],
            modified: array[i + 1]
        });
    }
    return filesList;
}

var remoteFiles = convertToListOfFiles(remoteArray);
var localFiles = convertToListOfFiles(localArray);
var filesToDownload = remoteFiles.filter(file => {
    let match = localFiles.find(localFile => localFile.name === file.name);
    // Download is needed if no local file matches this name or if its modification date is older than the remote one
    return !match || match.modified < file.modified;
});

console.log('Files to be downloaded or re-downloaded', filesToDownload);
// Each file in this list will be represented by an object { name, modified }

If you are unable to utilize features like Array.prototype.filter or arrow functions due to older browsers or Node versions, an alternative method to achieve filesToDownload would be:

var filesToDownload = [];
for (var i = 0; i < remoteFiles.length; i++) {
    var found;
    for (var j = 0; j < localFiles.length; j++) {
        if (remoteFiles[i].name === localFiles[j].name) {
            found = localFiles[j];
            break;
        }
    }
    if (!found || found.modified < remoteFiles[i].modified) {
        filesToDownload.push(found);
    }
}

Answer 2

To simplify the process, consider converting your data into a list of objects that represent each file. While this may not be the most efficient method, it will enhance clarity and ease of maintenance.

function convertToListOfFiles(array) {
    var filesList = [];
    for (var i = 0; i < array.length; i += 2) {
        filesList.push({
            name: array[i],
            modified: array[i + 1]
        });
    }
    return filesList;
}

var remoteFiles = convertToListOfFiles(remoteArray);
var localFiles = convertToListOfFiles(localArray);
var filesToDownload = remoteFiles.filter(file => {
    let match = localFiles.find(localFile => localFile.name === file.name);
    // Download is needed if no local file matches this name or if its modification date is older than the remote one
    return !match || match.modified < file.modified;
});

console.log('Files to be downloaded or re-downloaded', filesToDownload);
// Each file in this list will be represented by an object { name, modified }

If you are unable to utilize features like Array.prototype.filter or arrow functions due to older browsers or Node versions, an alternative method to achieve filesToDownload would be:

var filesToDownload = [];
for (var i = 0; i < remoteFiles.length; i++) {
    var found;
    for (var j = 0; j < localFiles.length; j++) {
        if (remoteFiles[i].name === localFiles[j].name) {
            found = localFiles[j];
            break;
        }
    }
    if (!found || found.modified < remoteFiles[i].modified) {
        filesToDownload.push(found);
    }
}

Answer 3

Answer №2

Here is a snippet of code that helps identify the files that need to be updated by comparing timestamps:

# Creating a dictionary to map each CDN file to its timestamp
cdn_files = {}
for i in range(0, len(Array1), 2):
    cdn_files[Array1[i]] = Array1[i + 1]

# Finding the files that need to be updated
files_to_update = []
for i in range(0, len(Array2), 2):
    file_path = Array2[i]
    # Checking if the file is in the CDN and if the timestamp is newer, then add to update list
    if file_path in cdn_files and cdn_files[file_path] > Array2[i + 1]:
        files_to_update.append(file_path)

Answer 4

Here is a snippet of code that helps identify the files that need to be updated by comparing timestamps:

# Creating a dictionary to map each CDN file to its timestamp
cdn_files = {}
for i in range(0, len(Array1), 2):
    cdn_files[Array1[i]] = Array1[i + 1]

# Finding the files that need to be updated
files_to_update = []
for i in range(0, len(Array2), 2):
    file_path = Array2[i]
    # Checking if the file is in the CDN and if the timestamp is newer, then add to update list
    if file_path in cdn_files and cdn_files[file_path] > Array2[i + 1]:
        files_to_update.append(file_path)

Search two arrays in a loop and identify variations with a unique approach

Answer №1

Answer №2

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