I need a function limitCalls (fn, maxCalls) that takes a function fn and returns a new function that can be called no more than the number of times specified in maxCalls. 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);
});
I have:
var calls = 0;
export default function limitCalls(fn, maxCalls) {
if (calls >= maxCalls) {
return undefined;
}
calls += 1;
return fn();
}
And error is limitedIncrementA is not a function. Help me please to realise it.
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');In this snippet, limitedIncrementA isn't indeed a function. See this:
/* You're calling makeIncrement,
so you're passing its return to 'limitCalls'
*/
const limitedIncrementA = limitCalls(makeIncrement(), 3);
/* Here, considering that makeIncrement exists,
you're passing a reference to this functions,
which can be called inside 'limitCalls'
*/
const limitedIncrementB = limitCalls(makeIncrement, 3);
So, supposing that makeIncrement returns 1, 2, 3, ..., your current code is equivalent to:
limitCalls(1, 3);