Why Does My `setTimeout` Function Execute Immediately Instead of After the Delay?

Unexpected Immediate Execution of setTimeout Function

In an effort to minimize server load by updating a web page value at regular intervals, a developer encounters an issue where the setTimeout() function behaves unexpectedly. Instead of executing after a specified delay, the function executes immediately.

Upon examination of the provided code snippet:

window.onload = function GetUsersNumber() {
    //...
    setTimeout(GetUsersNumber(), 50000);
}

The issue lies in how the setTimeout() function is called. In JavaScript, function calls are denoted by parentheses after the function name. However, in this case, the parentheses following GetUsersNumber() invoke the function immediately, rather than passing it as a reference.

To rectify this issue, remove the parentheses from the setTimeout() call, effectively passing the function object itself:

setTimeout(GetUsersNumber, 50000);

By doing so, setTimeout() can now correctly schedule the function to execute after the specified delay, allowing for the intended delayed update of the web page value without overwhelming the server.

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