combine.js

const combineMessages = (messages) => {
    let combined = []
    let params = { index: -1, groupDate: null, userId: null, lastBlock: -1 }
    for (let i = 0; i < messages.length; ++i) {
        let message = messages[i]
        let date = new Date(message.created_at)

        if (!params.groupDate || date.getDate() !== params.groupDate) {
            params.groupDate = date.getDate();
            params.runningDate = null;
            params.lastBlock = -1
            params.userId = null
            params.index = combined.push({ date: message.created_at, messages: [] }) - 1
        }

        if (!params.userId || params.userId !== message.user.id) {
            params.userId = message.user.id
            params.lastBlock = combined[params.index].messages.push({...message, children: []}) - 1
        }
        combined[params.index].messages[params.lastBlock].children.push(message)
    }
    return combined;
}