THE TASK Write a recursive function, sum(arr, n), that returns the sum of the first n elements of an array arr.
I dont understand why only 1 of the 5 tests are passing. And why the log is reporting: RangeError: Maximum call stack size exceeded. Ugh I hate recursion…
function sum(arr, n) {
// Only change code below this line
if (n <= 0) {
return 0;
}
return sum(arr, n - 1) + arr[n - 1];
// Only change code above this line
}
console.log(sum([1, 2, 3, 4, 5, 6, 7]), 6);
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Challenge: Basic JavaScript - Replace Loops using Recursion
As you were not passing a required param, js gave that param the value of undefined and that caused an unending series of recursive calls that overflowed the stack (and I guess prevented anything else from running)
Javascript does not care how many parameters you pass to a function, regardless of what you put in your declaration. It is up to you to decide what to do if parameters are missing or invalid.
If a parameter is missing, it will be undefined, so you could test for it with if (n === undefined) or if (isNaN(n)) (which should be true as long as n is not a number), then you could throw an error or assign the length of arr to n as a default value.
Here is another way that you could tell Javascript to warn you if a parameter is missing:
const isRequired = () => {
throw new Error('param is required');
};
function sum(arr, n = isRequired()) {
// Only change code below this line
if (n <= 0) {
return 0;
}
return sum(arr, n - 1) + arr[n - 1];
// Only change code above this line
}
console.log(sum([1, 2, 3, 4, 5, 6, 7])); // missing n