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patternjavascriptMinor

Checking two arrays for matches

Submitted by: @import:stackexchange-codereview··
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matchesarrayscheckingtwofor

Problem

Is there a better way to do this?

var duplicate = false;
    for (var i = 0; i < acceptedFiles.length; i++) {
        for (var j = 0; j < attachments.attachments.length; j++) {
            if (attachments.attachments[j].name === acceptedFiles[i].name) {
                duplicate = true;
            }
        }
    }

Solution

Presumably, once a duplicate is found you don't need to continue looping:

if (attachments.attachments[j].name === acceptedFiles[i].name) {
    duplicate = true;
}


With JavaScript, the best thing would be to wrap up your for loops in a function:

function containsDuplicate(acceptedFiles, attachments) {
    for (var i = 0; i < acceptedFiles.length; i++) {
        for (var j = 0; j < attachments.attachments.length; j++) {
            if (attachments.attachments[j].name === acceptedFiles[i].name) {
                return true;
            }
        }
    }
    return false;
}


As this is a problem that applies to multiple languages, look at the break keyword.

Code Snippets

if (attachments.attachments[j].name === acceptedFiles[i].name) {
    duplicate = true;
}
function containsDuplicate(acceptedFiles, attachments) {
    for (var i = 0; i < acceptedFiles.length; i++) {
        for (var j = 0; j < attachments.attachments.length; j++) {
            if (attachments.attachments[j].name === acceptedFiles[i].name) {
                return true;
            }
        }
    }
    return false;
}

Context

StackExchange Code Review Q#69617, answer score: 8

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