Hide Button on Missing Variable Value

Handling Undefined Values in Dynamic HTML Buttons with JavaScript

While working on a JavaScript project, I encountered an interesting situation where I needed to dynamically create table rows with buttons based on data fetched from an API. The data structure included various links represented under _links, each containing various relational navigation URLs like first, self, next, and last. These buttons were to simplify the navigation across different views or data pages. The crux of the task was to ensure that if any of these links were missing (for example, next or last), the corresponding button should be hidden to prevent user confusion or potential runtime errors.

Understanding the Challenge

To put it simply, when creating elements dynamically based on external data, there’s always a chance that some data points might be undefined. This often happens with navigational links in APIs where the next link might be undefined if you’re on the last page. The challenge is to conditionally render these buttons only when their associated links exist in the data.

JavaScript Implementation

Here’s how I approached the problem. I continued to use template literals for string construction, which are immensely helpful for embedding expressions within strings. However, the key was managing conditions right within these literals.

Here’s a modified version of the original loop code that now checks for the existence of each link before attempting to include the button in the HTML string:

let myTBody2 = "";

data._embedded.softwares.forEach(software => {
    myTBody2 += `
        <tr>
            <td>${software._links.first ? `<button class="btn btn-sm btn-primary" onclick="myFetcher('${software._links.first.href}')">First</button>` : ''}</td>
            <td>${software._links.self ? `<button class="btn btn-sm btn-primary" onclick="myFetcher('${software._links.self.href}')">Current</button>` : ''}</td>
            <td>${software._links.next ? `<button class="btn btn-sm btn-primary" onclick="myFetcher('${software._links.next.href}')">Next</button>` : ''}</td>
            <td>${software._links.last ? `<button class="btn btn-sm btn-primary" onclick="myFetcher('${software._links.last.href}')">Last</button>` : ''}</td>
        </tr>
    `;
});

// Append myTBody2 to your table body
document.querySelector("#your-table-body-id").innerHTML = myTBody2;

In this snippet, the ternary operator ? checks for the existence of each link (software._links.first, software._links.self, etc.). If the link exists, it renders the button with an onclick event handler that triggers myFetcher function passing the URL. If the link does not exist, it outputs an empty string, effectively hiding the button.

Advantages of This Approach

This solution leverages JavaScript’s flexibility with template literals and conditional (ternary) operators to make the code compact and readable. It eliminates the possibility of runtime errors due to undefined properties and enhances user experience by not displaying irrelevant options.

Moreover, the use of event handlers (onclick) directly ties each button to a specific functionality, making the table data-driven and interactive. By dynamically checking the presence of data and adjusting the UI accordingly, we cater to dynamic data conditions seamlessly.

This approach offers a fundamental and practical strategy to handling missing data in a way that keeps user interfaces robust and responsive to varying data states. By embedding logic directly within our HTML generation, we reduce the overall complexity and enhance maintainability.