Tips for restricting function invocations in JavaScript?

Question

Tips for restricting function invocations in JavaScript?

I am seeking a function called limitCalls(fn, maxCalls) which accepts a function fn and creates a new function that can only be called the specified number of times in maxCalls. Here is a test example:

 it('limitCalls', () => {
const makeIncrement = () => {
  let count = 0;

  return () => {
    count += 1;
    return count;
  };
};

const limitedIncrementA = limitCalls(makeIncrement(), 3);

expect(limitedIncrementA()).toBe(1);
expect(limitedIncrementA()).toBe(2);
expect(limitedIncrementA()).toBe(3);
expect(limitedIncrementA()).toBe(undefined);
expect(limitedIncrementA()).toBe(undefined);

const limitedIncrementB = limitCalls(makeIncrement(), 1);

expect(limitedIncrementB()).toBe(1);
expect(limitedIncrementB()).toBe(undefined);
expect(limitedIncrementB()).toBe(undefined);

});

This is my implementation so far:

var calls = 0;
export default function limitCalls(fn, maxCalls) {
  if (calls >= maxCalls) {
    return undefined;
  }
  calls += 1;
  return fn();
}

The error I am encountering is "limitedIncrementA is not a function." Please assist me with resolving this issue.

javascript function testing

Answer 1

Answer №1

Instead of conditionally returning a function, always return a function that conditionally executes the fn callback:

function limitCalls(fn, maxCalls) {
  let count = 0;
  
  return function(...args) {
    return count++ < maxCalls ? fn(...args) : undefined;
  }
}

const limited = limitCalls(console.log, 3);

limited('one');
limited('two');
limited('three');
limited('four');

Answer 2

Instead of conditionally returning a function, always return a function that conditionally executes the fn callback:

function limitCalls(fn, maxCalls) {
  let count = 0;
  
  return function(...args) {
    return count++ < maxCalls ? fn(...args) : undefined;
  }
}

const limited = limitCalls(console.log, 3);

limited('one');
limited('two');
limited('three');
limited('four');

Answer 3

Answer №2

Within this code snippet, it is important to note that limitedIncrementA does not function as expected. Take a look at the following details:

/* When you use makeIncrement in this context,
   the result is passed to 'limitCalls'
 */
const limitedIncrementA = limitCalls(makeIncrement(), 3);

/* In contrast, when you pass makeIncrement as is,
   you are providing a reference to the function itself
   that can be utilized within 'limitCalls'
 */
const limitedIncrementB = limitCalls(makeIncrement, 3);

Therefore, assuming that makeIncrement produces incremental values (1, 2, 3, ...), your current implementation is essentially like this:

limitCalls(1, 3);

Answer 4

Within this code snippet, it is important to note that limitedIncrementA does not function as expected. Take a look at the following details:

/* When you use makeIncrement in this context,
   the result is passed to 'limitCalls'
 */
const limitedIncrementA = limitCalls(makeIncrement(), 3);

/* In contrast, when you pass makeIncrement as is,
   you are providing a reference to the function itself
   that can be utilized within 'limitCalls'
 */
const limitedIncrementB = limitCalls(makeIncrement, 3);

Therefore, assuming that makeIncrement produces incremental values (1, 2, 3, ...), your current implementation is essentially like this:

limitCalls(1, 3);

Tips for restricting function invocations in JavaScript?

Answer №1

Answer №2

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