merge json array objects based on ID, Javascript

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//JavaScript-C24.2.0 (SpiderMonkey)

mergeArrayObjects([{"ASIN":12345,"Description":"Some description about ASIN 12345"},
                   {"ASIN":12347,"Title":"Title for ASIN 12347"},
                   {"ASIN":12346,"Title":"Title for ASIN 12346"},
                   {"ASIN":12347,"Description":"Some description about ASIN 12347"},
                   {"ASIN":12343,"Title":"Title for ASIN 12343"},
                   {"ASIN":12347,"Rank":"4"},
                   {"ASIN":12346,"Rank":"3"},
                   {"ASIN":12343,"Description":"Some description about ASIN 12343"},
                   {"ASIN":12345,"Title":"Title for ASIN 12345"},
                   {"ASIN":12348,"Description":"Some description about ASIN 12348"},
                   {"ASIN":12348,"Title":"Title for ASIN"},{"ASIN":12348,"Rank":"2"},
                   {"ASIN":12345,"Rank":"1"},
                   {"ASIN":12346,"Description":"Some description about ASIN 12346"},
                   {"ASIN":12344,"Description":"Some description about ASIN 12344"},
                   {"ASIN":12344,"Title":"Title for ASIN 12344"},
                   {"ASIN":12344,"Rank":"5"},
                   {"ASIN":12343,"Rank":"6"}]);

function mergeArrayObjects(array) {
    let hash = new Map();
    
    array.forEach((item)=> {
        var asin = item['ASIN'];
        var desc = item['Description'];
        var title = item['Title'];
        var rank = item['Rank'];
        let obj;
        
        if (hash.get(asin) != undefined) {
            obj = hash.get(asin);
        } else {
            obj = new Map();
        }
        obj.set('ASIN', asin);

if (desc != undefined) {
            obj.set('Description', desc);
        }
        if (title != undefined) {
            obj.set('Title', title);
        }
        if (rank != undefined) {
            obj.set('Rank', rank);
        }
        hash.set(asin, obj);
    });
    let merged = [];
    for (let [key, value] of hash) {
        merged.push(value);
    }
    merged.forEach(item=>{
        printMap(item);
        print('==================================');
    });
}

function printMap (map) {
    for (let [key, value] of map) {
        print(key + ' : ' + value);
    }
}

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Absolute running time: 0.1 sec, cpu time: 0.06 sec, memory peak: 6 Mb, absolute service time: 0,11 sec