1.8 KiB
1.8 KiB
title | id | challengeType |
---|---|---|
Accumulator factory | 594810f028c0303b75339ace | 5 |
Description
Create a function that takes a single (numeric) argument and returns another function that is an accumulator. The returned accumulator function in turn also takes a single numeric argument, and returns the sum of all the numeric values passed in so far to that accumulator (including the initial value passed when the accumulator was created).
Rules:
Do not use global variables.
Hint:
Closures save outer state.
Instructions
Tests
tests:
- text: <code>accumulator</code> is a function.
testString: assert(typeof accumulator === 'function', '<code>accumulator</code> is a function.');
- text: <code>accumulator(0)</code> should return a function.
testString: assert(typeof accumulator(0) === 'function', '<code>accumulator(0)</code> should return a function.');
- text: <code>accumulator(0)(2)</code> should return a number.
testString: assert(typeof accumulator(0)(2) === 'number', '<code>accumulator(0)(2)</code> should return a number.');
- text: Passing in the values 3, -4, 1.5, and 5 should return 5.5.
testString: assert(testFn(5) === 5.5, 'Passing in the values 3, -4, 1.5, and 5 should return 5.5.');
Challenge Seed
function accumulator (sum) {
// Good luck!
}
After Test
const testFn = typeof accumulator(3) === 'function' && accumulator(3);
if (testFn) {
testFn(-4);
testFn(1.5);
}
Solution
function accumulator (sum) {
return function (n) {
return sum += n;
};
}