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Chalarangelo/arrayAdvancedReduce.js

Created September 14, 2017 09:18
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  1. Chalarangelo created this gist Sep 14, 2017.
    69 changes: 69 additions & 0 deletions arrayAdvancedReduce.js
    View file
    Original file line number Diff line number Diff line change
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    // An array of articles with their tags.
    var articles = [
    {title: "Introduction to Javascript Scope", tags: [ "Javascript", "Variables", "Scope"]},
    {title: "Javascript Closures", tags: [ "Javascript", "Variables", "Closures"]},
    {title: "A Guide to PWAs", tags: [ "Javascript", "PWA"]},
    {title: "Javascript Functional Programming Examples", tags: [ "Javascript", "Functional", "Function"]},
    {title: "Why Javascript Closures are Important", tags: [ "Javascript", "Variables", "Closures"]},
    ];

    // A function that reduces the above array to an
    // array based on tags.
    var tagView = function(accumulator, x){
    // For every tag in the article's tag array
    x.tags.forEach(function(currentTag){
    // Create a function to check if it matches
    var findCurrentTag = function(y) { return y.tag == currentTag; };
    // Check if it's already in the accumulator array
    if (accumulator.some(findCurrentTag)){
    // Find it and get its index
    var existingTag = accumulator.find(findCurrentTag);
    var existingTagIndex = accumulator.findIndex(findCurrentTag);
    // Update the number and array of articles
    accumulator[existingTagIndex].count += 1;
    accumulator[existingTagIndex].articles.push(x.title);
    }
    // Otherwise add the tag to the accumulator array
    else {
    accumulator.push({tag: currentTag, count: 1, articles: [x.title]});
    }
    });
    // Return the accumulator array
    return accumulator;
    }

    // Transform the original array
    articles.reduce(tagView,[]);
    // Output:
    /*
    [
    {tag: "Javascript", count: 5, articles: [
    "Introduction to Javascript Scope",
    "Javascript Closures",
    "A Guide to PWAs",
    "Javascript Functional Programming Examples",
    "Why Javascript Closures are Important"
    ]},
    {tag: "Variables", count: 3, articles: [
    "Introduction to Javascript Scope",
    "Javascript Closures",
    "Why Javascript Closures are Important"
    ]},
    {tag: "Scope", count: 1, articles: [
    "Introduction to Javascript Scope"
    ]},
    {tag: "Closures", count: 2, articles: [
    "Javascript Closures",
    "Why Javascript Closures are Important"
    ]},
    {tag: "PWA", count: 1, articles: [
    "A Guide to PWAs"
    ]},
    {tag: "Functional", count: 1, articles: [
    "Javascript Functional Programming Examples"
    ]},
    {tag: "Function", count: 1, articles: [
    "Javascript Functional Programming Examples"
    ]}
    ]
    */