Generate day-of-the-week objects from an array of strings

Question

I have an array of day ranges, like this:

["Mon-Tue", "Mon-Wed", "Mon-Thu", "Mon-Fri", "Mon-Sat", "Mon-Sun", "Tue-Mon", "Tue-Wed", "Tue-Thu", "Tue-Fri", "Tue-Sat", "Tue-Sun", ...]

What I need is to create a large object which maps each one of these strings to an array containing all the relevant days, like this:

var object = {
  'Mon-Tue': ['Mon', 'Tue'],
  'Mon-Wed': ['Mon', 'Tue', 'Wed'],
}

To help, I have an array of the possible days:

var days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']

Is this possible without doing it all manually?

Thanks!

Answer 1

You could take a Map for getting days with an index and iterate until you got all days.

var days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'],
    daysMap = new Map(days.map((d, i) => [d, i])),
    data = ["Mon-Tue", "Mon-Wed", "Mon-Thu", "Mon-Fri", "Mon-Sat", "Mon-Sun", "Tue-Mon", "Tue-Wed", "Tue-Thu", "Tue-Fri", "Tue-Sat", "Tue-Sun"],
    result = Object.assign({}, ...data.map(d => {
        var [start, end] = d.split('-'),
            temp = [],
            s = daysMap.get(start),
            e = daysMap.get(end);

        while (s !== e) {
            temp.push(days[s]);
            s++;
            s %= days.length
        }
        temp.push(days[s]);
        return { [d]: temp };
    }));

console.log(result);

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If you like, you could take a Generator for the wanted days.

function* getDays(from, to) {
    var days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'],
        i = days.indexOf(from);

    while (days[i % days.length] !== to) yield days[i++ % days.length];
    yield days[i % days.length];
}

var data = ["Fri-Tue", "Mon-Tue", "Mon-Wed", "Mon-Thu", "Mon-Fri", "Mon-Sat", "Mon-Sun", "Tue-Mon", "Tue-Wed", "Tue-Thu", "Tue-Fri", "Tue-Sat", "Tue-Sun"],
    result = Object.assign({}, ...data.map(d => ({ [d]: [...getDays(...d.split('-'))] })));

console.log(result);

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Another approach by using a tomorrow object, which gives the day of tomorrow.

function* getDays(from, to) {
    var tomorrow = { Sun: 'Mon', Mon: 'Tue', Tue: 'Wed', Wed: 'Thu', Thu: 'Fri', Fri: 'Sat', Sat: 'Sun' };

    yield from;
    while (from !== to) yield from = tomorrow[from];
}

var data = ["Fri-Tue", "Mon-Tue", "Mon-Wed", "Mon-Thu", "Mon-Fri", "Mon-Sat", "Mon-Sun", "Tue-Mon", "Tue-Wed", "Tue-Thu", "Tue-Fri", "Tue-Sat", "Tue-Sun"],
    result = Object.assign({}, ...data.map(d => ({ [d]: [...getDays(...d.split('-'))] })));

console.log(result);

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