How to Implement Single-Use JavaScript Functions?

Implementing a Single-Use JavaScript Function

In JavaScript, it's sometimes desirable to create a function that can be executed only once. While static variables can achieve this in languages like C and Java, JavaScript offers more elegant solutions.

Closure-Based Implementation

A closure, which encapsulates a variable within a function, can effectively prevent a function from being executed multiple times. The following code snippet demonstrates this approach:

<code class="javascript">var something = (function() {
  var executed = false;
  return function() {
    if (!executed) {
      executed = true;
      // Execute the desired actions
    }
  };
})();</code>

By calling something(), the function will be invoked once and set the executed flag to true. Subsequent calls to the function will have no effect since executed is already true.

Once() Utility Function

Many JavaScript libraries, such as Underscore and Ramda, provide a once() utility function that serves this purpose. The following code shows how to use the once() function from Lodash:

<code class="javascript">import { once } from "lodash";

function something() {
  // Execute actions
}

const one_something = once(something);

one_something(); // Executes something
one_something(); // No effect</code>

Custom Once() Function

If not using a library, you can easily implement your own once() function:

<code class="javascript">function once(fn, context) {
  var result;
  return function() {
    if (fn) {
      result = fn.apply(context || this, arguments);
      fn = null;
    }
    return result;
  };
}</code>

This function wraps the given function fn and ensures it is called only once, caching the returned value for subsequent calls.

By leveraging closures or utility functions, you can create JavaScript functions that execute only once, providing a convenient and versatile approach for various use cases.

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