Dynamically generating HTML elements based on user input or specific conditions is a common requirement in web development. One such scenario is creating time dropdowns that adjust their options based on the current time, desired range, and intervals. This article presents a JavaScript or jQuery solution for creating dynamic time dropdowns within a select form element.
Why Dynamic Time Dropdowns?
Dynamic time dropdowns are helpful in many situations:
Scheduling appointments: Allow users to select time slots that adjust based on real-time availability.
Booking services: Provide time options for services only offered during specific hours or at certain intervals.
Setting reminders: Enable users to set reminders with flexible time options, starting from the current time or within a specific range.
Improved user experience: Present users with relevant time choices, avoiding unnecessary scrolling and confusion.
Dynamic Time Solution Using JavaScript
The JavaScript solution below enables you to create dynamic time dropdown menus on your web pages. These menus adapt to different scenarios and provide users with relevant time choices.
Here’s what it offers:
Flexible Time Ranges: Define the starting and ending times for the dropdown options. You can even use the current time to dynamically start or end the options at the current time.
Customizable Intervals: Set the intervals between time options, whether every 15 minutes, 30 minutes, or any other duration.
Varied Display Formats: Control how the time is displayed, choosing between 12-hour or 24-hour formats with AM/PM indicators as needed.
Start from Now: Configure the dropdown to begin with the current time, making it ideal for scheduling or booking scenarios.
Full-Day Coverage: If no specific time range is provided, the dropdown will default to offering options for the entire day.
Smart Empty Handling: If no valid time options can be generated based on the given parameters, the dropdown will be automatically disabled to prevent user confusion.
This solution enhances user experience by presenting only relevant time choices, eliminating unnecessary scrolling and making interactions smoother. Whether you’re building a scheduling application, a booking system, or any other feature that requires time selection, this JavaScript code provides the flexibility and control you need.
Dynamic Time Examples
Example 1: Full Day, 30-minute intervals, 24-hour format
Example 2: Start from Now, End at 8 PM, 15-minute intervals, 12-hour format
Example 3: Start at 10 AM, End at Now, 1-hour intervals, 24-hour format
Example 4: Start at 2 PM, End at 6 PM, 10-minute intervals, 12-hour format with lowercase AM/PM
Example 5: Start now until before midnight with 30 minute intervals
</select>
Dynamic Time JavaScript
Here’s the complete JavaScript code for creating dynamic time dropdowns:
function getTime(from, to, interval, startNow, format, timeSelect) {
var select = ‘<option value=””>Select a Time</option>’;
var now = new Date();
var currentHour = now.getHours();
var currentMinute = now.getMinutes();
var optionsCount = 0;
if (from === “now”) {
from = currentHour;
} else if (from === “”) {
from = 0;
} else {
from = parseInt(from);
}
if (to === “now”) {
to = currentHour;
} else if (to === “”) {
to = 23;
} else {
to = parseInt(to);
}
if (startNow) {
if (from < currentHour) {
from = currentHour;
}
if (to < currentHour) {
to = currentHour;
}
}
for (var hour = from; hour <= to; hour++) {
var hour12 = hour > 12 ? hour – 12 : hour;
hour12 = hour12 === 0 ? 12 : hour12; // Change 0 to 12 for 12 AM
var ampm = hour >= 12 ? ‘PM’ : ‘AM’;
for (var min = 0; min < 60; min += interval) {
if (startNow && hour === currentHour && min < currentMinute) {
continue;
}
var min0 = min < 10 ? ‘0’ + min : min;
var date = new Date();
date.setHours(hour);
date.setMinutes(min);
var value = formatDate(date, format);
select += ‘<option value=”‘ + value + ‘”>’ + hour12 + ‘:’ + min0 + ‘ ‘ + ampm + ‘</option>’;
optionsCount++;
}
}
timeSelect.innerHTML = select;
if (optionsCount <= 1) {
timeSelect.disabled = true;
}
}
function formatDate(date, format) {
var hours = date.getHours();
var minutes = date.getMinutes();
var ampm = hours >= 12 ? ‘PM’ : ‘AM’;
hours = hours % 12;
hours = hours ? hours : 12; // the hour ‘0’ should be ’12’
minutes = minutes < 10 ? ‘0’+minutes : minutes;
var strTime = hours + ‘:’ + minutes + ‘ ‘ + ampm;
return format
.replace(/H/g, date.getHours())
.replace(/h/g, hours)
.replace(/i/g, minutes)
.replace(/s/g, date.getSeconds())
.replace(/a/g, ampm.toLowerCase())
.replace(/A/g, ampm);
}
var timeSelects = document.querySelectorAll(‘.timeSelect’);
timeSelects.forEach(function(timeSelect) {
var from = timeSelect.dataset.from;
var to = timeSelect.dataset.to;
var interval = parseInt(timeSelect.dataset.interval);
var startNow = timeSelect.dataset.startNow === ‘true’;
var format = timeSelect.dataset.format;
getTime(from, to, interval, startNow, format, timeSelect);
});
Breaking Down the Code
Now, let’s break down the code for our readers:
1. HTML Structure:
We use <select> elements with the class timeSelect to create the dropdown menus.
Each select has data attributes:
data-from: The starting hour (or “now”).
data-to: The ending hour (or “now”).
data-interval: The interval in minutes.
data-start-now: Whether to start from the current time.
data-format: The time format (e.g., “H:i”, “h:i A”).
2. JavaScript Functions:
getTime(from, to, interval, startNow, format, timeSelect):
This function does the heavy lifting. It takes the parameters from the data attributes and the select element itself.
It calculates the time range based on from and to, considering the startNow option and the current time.
It generates the time options with the specified interval.
It formats the time values using the formatDate() function.
It populates the given select element with the generated options.
It disables the select if there are no valid options.
formatDate(date, format):
This helper function formats the date object according to the provided format string, similar to PHP date formatting.
3. Initialization:
The code selects all elements with the class timeSelect using querySelectorAll().
It then loops through each select element using forEach().
For each select, it retrieves the parameters from the data attributes.
It calls the getTime() function with the parameters and the select element to generate and populate the options.
Dynamic Time jQuery
If you’re utilizing jQuery, here’s the solution rewritten.
function getTime(from, to, interval, startNow, format, $timeSelect) {
var selectOptions = ‘<option value=””>Select a Time</option>’;
var now = new Date();
var currentHour = now.getHours();
var currentMinute = now.getMinutes();
var optionsCount = 0;
if (from === “now”) {
from = currentHour;
} else if (from === “”) {
from = 0;
} else {
from = parseInt(from);
}
if (to === “now”) {
to = currentHour;
} else if (to === “”) {
to = 23;
} else {
to = parseInt(to);
}
if (startNow) {
if (from < currentHour) {
from = currentHour;
}
if (to < currentHour) {
to = currentHour;
}
}
for (var hour = from; hour <= to; hour++) {
var hour12 = hour > 12 ? hour – 12 : hour;
hour12 = hour12 === 0 ? 12 : hour12;
var ampm = hour >= 12 ? ‘PM’ : ‘AM’;
for (var min = 0; min < 60; min += interval) {
if (startNow && hour === currentHour && min < currentMinute) {
continue;
}
var min0 = min < 10 ? ‘0’ + min : min;
var date = new Date();
date.setHours(hour);
date.setMinutes(min);
var value = formatDate(date, format);
selectOptions += ‘<option value=”‘ + value + ‘”>’ + hour12 + ‘:’ + min0 + ‘ ‘ + ampm + ‘</option>’;
optionsCount++;
}
}
$timeSelect.html(selectOptions);
if (optionsCount <= 1) {
$timeSelect.prop(‘disabled’, true);
}
}
function formatDate(date, format) {
var hours = date.getHours();
var minutes = date.getMinutes();
var ampm = hours >= 12 ? ‘PM’ : ‘AM’;
hours = hours % 12;
hours = hours ? hours : 12;
minutes = minutes < 10 ? ‘0’+minutes : minutes;
var strTime = hours + ‘:’ + minutes + ‘ ‘ + ampm;
return format
.replace(/H/g, date.getHours())
.replace(/h/g, hours)
.replace(/i/g, minutes)
.replace(/s/g, date.getSeconds())
.replace(/a/g, ampm.toLowerCase())
.replace(/A/g, ampm);
}
$(document).ready(function() {
$(‘.timeSelect’).each(function() {
var $timeSelect = $(this);
var from = $timeSelect.data(‘from’);
var to = $timeSelect.data(‘to’);
var interval = parseInt($timeSelect.data(‘interval’));
var startNow = $timeSelect.data(‘start-now’) === true;
var format = $timeSelect.data(‘format’);
getTime(from, to, interval, startNow, format, $timeSelect);
});
});
This approach allows multiple time dropdowns on the same page, each with its configuration and behavior. The code handles various scenarios, including full-day selections, starting from the current time and different time formats, providing a flexible and user-friendly solution for dynamic time selection.
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Originally Published on Martech Zone: Dynamically Generate a Time Select Dropdown with Intervals (Javascript or jQuery)