表示/非表示ボタンを最初にアクティブにするときにダブルクリックが必要なのはなぜですか?

Why My Show/Hide Button Requires a Double-Click on First Use

In this JavaScript code, a button exists to control the visibility of an element (#menu) on a website. However, upon the first click, the button inexplicably requires a double-click to toggle the element's visibility. This behavior may occur due to an oversight in the display style checking before toggling the element's visibility.

When JavaScript accesses the style property of an element, it may return an empty string if the style is not explicitly set inline. In this case, the code initially checks if the x.style.display is equal to "none." However, this check does not account for the possibility that the element's display style may simply be empty.

To remedy this issue and ensure that the button shows the element with a single click on the first time, the code should be modified to check for an empty display style as well:

<code class="js">if (x.style.display === "none" || x.style.display === "") {
  x.style.display = "block";
} else {
  x.style.display = "none";
}</code>

By including the check for an empty display style, the code comprehensively handles all cases where the element's visibility is not explicitly set inline. Consequently, the button will now consistently toggle the element's visibility with a single click, even on the first use.

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