Sort a javascript array into nested arrays based on values

Question

I have an array of file names like so:

var filesArray = [
    "120.png",
    "120s.png",
    "120t.jpg",
    "169.png",
    "169r.jpg",
    "169s.jpg",
    "169t.jpg",
    "170.png",
    "170r.jpg",
    "170s.jpg",
    "170t.jpg",
]

Using javascript (es5 or 6 or 7 does not matter since I am using babel) I would like to sort it into a nested array like so:

[
    [
        "120.png",
        "120s.png",
        "120t.jpg"
    ],
    [
        "170.png",
        "170r.jpg",
        "170s.jpg",
        "170t.jpg"
    ]
]

I know that in order to find the same base names I have to run regex and I am already using filesArray[i].slice(0, -4).replace(/[^0-9\\.]/g, '') )

What I don't know however is how to run array.sort or array.map to get the final neste array.

By the way, it's long list of file names, and I would prefer the fastest most efficient way to do so without mutating the original array.

Answer 1

You could use a Map for grouping the items.

 var filesArray = ["120.png", "120s.png", "120t.jpg", "169.png", "169r.jpg", "169s.jpg", "169t.jpg", "170.png", "170r.jpg", "170s.jpg", "170t.jpg"], grouped = []; filesArray.forEach(function (a) { var key = a.slice(0, -4).replace(/[^0-9\\.]/g, ''), array = this.get(key); if (!array) { array = []; this.set(key, array); grouped.push(array); } array.push(a); }, new Map); console.log(grouped); 

 .as-console-wrapper { max-height: 100% !important; top: 0; } 

Answer 2

 var filesArray = ["120.png", "120s.png", "120t.jpg", "169.png", "169r.jpg", "169s.jpg", "169t.jpg", "170.png", "170r.jpg", "170s.jpg", "170t.jpg"]; var result = []; var obj = filesArray.reduce(function(prev, curr, index, array) { var rawName = curr.match(/[0-9]/g); if (rawName.length) { var name = rawName.join(''); if (prev[name]) { prev[name].push(curr); } else { prev[name] = [curr]; } } return prev }, {}); Object.keys(obj).forEach(function(key) { result.push(obj[key]); }); console.log(result); 

 .as-console-wrapper { max-height: 100% !important; top: 0; } .as-console-row, .as-console-row-code { background-color: #fff!important; }