Caches a function call to be in lazily invoked just once.

once.js

/**
 * Takes a function a lazily runs it once when invoked.
 *
 * Returns cached return value to subsequent calls.
 * Return value will always have reference equality with subsequent calls.
 *
 * @param {function} func - Function to run Once
 * @return {function}
 */
export default function once(func) {
    const neverRan = Symbol();
    let cacheReturn = neverRan;

    return function onceRun(...args) {
        if (cacheReturn === neverRan) {
            cacheReturn = func(...args);
        }

        return cacheReturn;
    };
}

Tiny Version

const once = (func) => {
	let neverRan = Symbol(), cacheReturn = neverRan;
	return (...args) => (cacheReturn !== neverRan || (cacheReturn = func(...args))) && cacheReturn;
}