Function startOf

tests/test_code/js/moment/moment.js:4075–4136

(units)

    }

    function startOf(units) {
        var time, startOfDate;
        units = normalizeUnits(units);
        if (units === undefined || units === 'millisecond' || !this.isValid()) {
            return this;
        }

        startOfDate = this._isUTC ? utcStartOfDate : localStartOfDate;

        switch (units) {
            case 'year':
                time = startOfDate(this.year(), 0, 1);
                break;
            case 'quarter':
                time = startOfDate(
                    this.year(),
                    this.month() - (this.month() % 3),
                    1
                );
                break;
            case 'month':
                time = startOfDate(this.year(), this.month(), 1);
                break;
            case 'week':
                time = startOfDate(
                    this.year(),
                    this.month(),
                    this.date() - this.weekday()
                );
                break;
            case 'isoWeek':
                time = startOfDate(
                    this.year(),
                    this.month(),
                    this.date() - (this.isoWeekday() - 1)
                );
                break;
            case 'day':
            case 'date':
                time = startOfDate(this.year(), this.month(), this.date());
                break;
            case 'hour':
                time = this._d.valueOf();
                time -= mod$1(
                    time + (this._isUTC ? 0 : this.utcOffset() * MS_PER_MINUTE),
                    MS_PER_HOUR
                );
                break;
            case 'minute':
                time = this._d.valueOf();
                time -= mod$1(time, MS_PER_MINUTE);
                break;
            case 'second':
                time = this._d.valueOf();
                time -= mod$1(time, MS_PER_SECOND);
                break;
        }