Function addLevelTicks

src/scale/Time.ts:543–640

(
        unitName: TimeUnit,
        lastLevelTicks: InnerTimeTick[],
        levelTicks: InnerTimeTick[]
    )

    }

    function addLevelTicks(
        unitName: TimeUnit,
        lastLevelTicks: InnerTimeTick[],
        levelTicks: InnerTimeTick[]
    ) {
        const newAddedTicks: ScaleTick[] = [];
        const isFirstLevel = !lastLevelTicks.length;

        if (isPrimaryUnitValueAndGreaterSame(getPrimaryTimeUnit(unitName), extent[0], extent[1], isUTC)) {
            return;
        }

        if (isFirstLevel) {
            lastLevelTicks = [{
                value: getFirstTimestampOfUnit(extent[0], unitName, isUTC),
            }, {
                value: extent[1]
            }];
        }

        for (let i = 0; i < lastLevelTicks.length - 1; i++) {
            const startTick = lastLevelTicks[i].value;
            const endTick = lastLevelTicks[i + 1].value;
            if (startTick === endTick) {
                continue;
            }

            let interval: number;
            let getterName: JSDateGetterNames;
            let setterName: JSDateSetterNames;
            let isDate = false;

            switch (unitName) {
                case 'year':
                    interval = Math.max(1, Math.round(approxInterval / ONE_DAY / 365));
                    getterName = fullYearGetterName(isUTC);
                    setterName = fullYearSetterName(isUTC);
                    break;
                case 'half-year':
                case 'quarter':
                case 'month':
                    interval = getMonthInterval(approxInterval);
                    getterName = monthGetterName(isUTC);
                    setterName = monthSetterName(isUTC);
                    break;
                case 'week':    // PENDING If week is added. Ignore day.
                case 'half-week':
                case 'day':
                    interval = getDateInterval(approxInterval, 31); // Use 32 days and let interval been 16
                    getterName = dateGetterName(isUTC);
                    setterName = dateSetterName(isUTC);
                    isDate = true;
                    break;
                case 'half-day':
                case 'quarter-day':
                case 'hour':
                    interval = getHourInterval(approxInterval);
                    getterName = hoursGetterName(isUTC);