onetime

Ensuring a function is only called once

This feature allows you to wrap a function with 'onetime' to ensure it can only be executed once. Subsequent calls to the function will have no effect.

const onetime = require('onetime');

const initialize = onetime(() => {
  console.log('Initialization complete.');
});

initialize(); // 'Initialization complete.'
initialize(); // No output, function not called again

Throwing an error on subsequent calls

This feature allows you to configure 'onetime' to throw an error if the function is attempted to be called more than once, which can be useful for debugging.

const onetime = require('onetime');

const doOnce = onetime(() => {
  console.log('Done once.');
}, {throw: true});

doOnce(); // 'Done once.'
try {
  doOnce(); // Throws an Error because the function was already called.
} catch (e) {
  console.error(e.message); // 'Function can only be called once.'
}

Checking if a function has been called

This feature provides a way to check if the onetime-wrapped function has been called, which can be useful for conditional logic based on whether the initialization or setup has already been performed.

const onetime = require('onetime');

const onceFn = onetime(() => {});

console.log(onetime.called(onceFn)); // false
onceFn();
console.log(onetime.called(onceFn)); // true