如何使用对象和数组操作实现连续相同项合并算法？

let arr = [
    { "start": 1, "end": 2, "content": ["A", "B", "E"] },
    { "start": 2, "end": 3, "content": ["B", "C"] },
    { "start": 3, "end": 4, "content": ["B", "D"] },
    { "start": 4, "end": 5, "content": ["D"] },
    { "start": 7, "end": 8, "content": ["B"] },
    { "start": 9, "end": 11, "content": ["B", "C"] }
];

let obj = {};
let list = arr.reduce((list, item, index, arr) => {
    item.content.forEach(citem => {
        let i = index;
        let next, cindex;
        while ((next = arr[i + 1]) && arr[i].end === next.start && (cindex = next.content.indexOf(citem)) >= 0) {
            i++;
            next.content.splice(cindex, 1);
        }
        let end = arr[i].end;
        let key = item.start + '-' + end;
        if (!obj[key]) {
            list.push(obj[key] = {
                start: item.start,
                end,
                content: [citem]
            });
        } else {
            obj[key].content.push(citem);
        }
    });
    return list;
}, []);

console.log(list);