JavaScript: Should I declare a variable based on a conditional evaluation?

I’m relatively new to JavaScript, and I encountered this code that puzzled me:

let proxySettings = document.getElementById('network.proxy.share_proxy_settings');
proxySettings.disabled = proxyModeSelection.value !== '1';

Wouldn’t it make more sense to evaluate proxyModeSelection.value using an if statement first, and then declare the variable inside that block only when it’s necessary? Additionally, I find this structure much less readable compared to traditional if statements with clear blocks of code for actions.

As an update, based on helpful feedback, this snippet originates from Firefox 3. In the Connect preferences of Firefox, selecting different proxy modes with radio buttons triggers the enablement or disablement of various form fields.

When deciding whether to use a direct assignment or an if statement in JavaScript, the primary considerations should be readability, maintainability, and the logic's complexity. The snippet you provided:

proxySettings.disabled = proxyModeSelection.value !== '1';

is an example of a concise and efficient approach suitable for straightforward conditions. This pattern is beneficial for simple scenarios where a variable has a direct correlation with a condition. However, when clarity is crucial, especially for those new to JavaScript or when dealing with more intricate logic, a traditional if statement can often be more explicit:

let proxySettings = document.getElementById('network.proxy.share_proxy_settings');
if (proxyModeSelection.value === '1') {
    proxySettings.disabled = false;
} else {
    proxySettings.disabled = true;
}

What's notable here is using an if-else block which makes the code clearer by explicitly defining the condition and outcomes. This can be especially useful in scenarios where the logic might grow or change, ensuring future maintainability. Ultimately, the choice between these strategies depends on whether prioritizing conciseness or readability enhances the overall code understanding for your specific case.

While structuring your code using a traditional if statement might seem clearer, the approach in your snippet serves a specific purpose: conciseness and readability, particularly for simple conditions. Here's a breakdown:

Using a direct assignment like:

proxySettings.disabled = proxyModeSelection.value !== '1';

allows you to handle the condition in a single line. This can be beneficial for straightforward logic where a variable's state is directly determined by a condition. It's particularly efficient in forms or UI scripts where reactivity is prioritized.

However, if readability and clarity are a priority, particularly for beginners or more complex logic, using an if statement like this might be better:

let proxySettings = document.getElementById('network.proxy.share_proxy_settings');
if (proxyModeSelection.value !== '1') {
    proxySettings.disabled = true;
} else {
    proxySettings.disabled = false;
}

This approach can improve readability by clearly showing each potential action. It's all about balancing readability and conciseness based on the context and the complexity of the logic.