If you’ve been working with Blazor, chances are you’ve found a need to enhance your applications by integrating JavaScript functions. Blazor provides great tools for building web apps using .NET, but JavaScript can significantly improve user experience and interactive features.
When building dynamic tables in Blazor, JavaScript integration is particularly helpful. For instance, JavaScript provides straightforward solutions for filtering, sorting, and handling interactive table events smoothly and efficiently.
How to Set Up a Table with Filtering in Blazor
Creating a table in a Blazor application starts straightforward. Suppose you want to display a dynamic list of customers. You’d typically bind your table to some sort of collection.
Here’s a simple example of a basic table structure in Blazor:
<table class="table">
<thead>
<tr>
<th>Name</th>
<th>Email</th>
<th>Phone</th>
</tr>
<tr>
<th><input @oninput="(e) => FilterTable(e, 'Name')" placeholder="Filter Name..." /></th>
<th><input @oninput="(e) => FilterTable(e, 'Email')" placeholder="Filter Email..." /></th>
<th><input @oninput="(e) => FilterTable(e, 'Phone')" placeholder="Filter Phone..." /></th>
</tr>
</thead>
<tbody>
@foreach(var customer in FilteredCustomers)
{
<tr>
<td>@customer.Name</td>
<td>@customer.Email</td>
<td>@customer.Phone</td>
</tr>
}
</tbody>
</table>
In the above example, header inputs allow users to filter data instantly. Whenever the user types into these fields, Blazor can trigger the filtering logic.
Implementing Filtering with JavaScript
While Blazor efficiently manages UI updates, sometimes JavaScript offers quicker DOM interactions. This is especially true when building highly interactive filtering experiences.
Let’s say you decide to implement instant filtering by integrating JavaScript into your Blazor app. A simple JavaScript filter might look something like this:
Create a JavaScript function like:
function filterTable(columnName, filterValue) {
let table = document.getElementById("yourTableId");
let rows = table.getElementsByTagName("tr");
for (let i = 1; i < rows.length; i++) {
let cols = rows[i].getElementsByTagName("td");
let cellValue = cols[columnName].innerText || cols[columnName].textContent;
rows[i].style.display = cellValue.toLowerCase()
.indexOf(filterValue.toLowerCase()) > -1 ? "" : "none";
}
}
Then, from your Blazor input box, simply call this function using JavaScript Interop:
@inject IJSRuntime JS
private async Task FilterTable(ChangeEventArgs e, string column)
{
await JS.InvokeVoidAsync("filterTable", columnIndexMap[column], e.Value?.ToString() ?? "");
}
Here, JavaScript interoperability (JS Interop) in Blazor allows .NET and JavaScript to work together seamlessly.
The Issue: JavaScript Not Detecting Delete Key to Clear Filter
However, you’ve probably run into a common problem while implementing filtering: the delete key is sometimes not detected correctly, especially when trying to clear the filter field entirely.
Typically, a user who tries deleting text to clear a filter expects the table to reset and show all data. Unfortunately, some JavaScript events, such as keypress or input events, don’t always capture the action neatly when users rapidly delete content in quick succession or when they clear the whole input.
I encountered this exact issue recently. Watching users get frustrated because the table wasn’t updating reliably wasn’t ideal. I initially tried adding basic event listeners in JavaScript to detect “keyup”, “keydown”, and “input” events:
document.querySelectorAll('input').forEach(input => {
input.addEventListener('keyup', (event) => {
if(event.key === 'Delete' || event.key === 'Backspace'){
filterTable(columnIndex, event.target.value);
}
});
});
However, despite adding these listeners, the delete key wasn’t consistently triggering the filter update as intended.
Solutions to Detect Delete Key for Clearing Filters in Blazor
After digging deeper, I found the real culprit was simpler: the “input” event itself is generally reliable for this scenario because it fires whenever the content of an input changes directly.
Here’s how I solved this issue effectively:
- Instead of relying on “keyup”, switch entirely to the more reliable “input” event to track any changes regardless of the key pressed.
- Use Blazor’s built-in @oninput event directly on your filter inputs. It inherently captures immediate changes, including text deletion.
- Trigger your JavaScript filtering function immediately in response to this event.
For instance, changing to the following will consistently detect deletions:
<input @oninput="(e) => FilterTable(e, 'Name')" placeholder="Filter Name..." />
Because “@oninput” detects every small change—even clearing the input—this approach resolved the delete-key detection problem.
Troubleshooting and Ensuring Stability
It’s crucial to thoroughly test these changes. Here’s a checklist for effective troubleshooting:
- Make sure the input event triggers consistently on all browsers.
- Check JavaScript console errors (MDN Web Docs) to address unexpected issues.
- Verify filter behavior thoroughly—rapid typing, quick deletions, and completely erasing input values.
After careful testing, this approach worked smoothly across major browsers like Chrome, Firefox, and Edge.
Improving this implementation further, consider adding “debounce” logic if your data set is large or if the filtering process is resource-intensive, as described in my previous article on JavaScript optimization methods.
Additional Tips and Resources
If you’re interested in further improving table filtering functionality in Blazor and JavaScript, consider these additional tips:
- Use debounce functions to prevent too many simultaneous filter processes.
- Add accessibility features to your filter inputs.
- Consider server-side paging for large datasets.
To take your JavaScript and Blazor skills further, explore these resources:
- Official Microsoft Blazor documentation: JavaScript Interop
- Stack Overflow threads on handling dynamic table filtering: Blazor questions
- Understanding DOM events: MDN Event Reference
Have you faced similar challenges integrating JavaScript into Blazor projects? Let me know your experiences or any other issues you’ve encountered in the comments below!
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