Published at Jul 13 2018
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Instructions

Test suite

Solution

Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.

The square of the sum of the first ten natural numbers is (1 + 2 + ... + 10)² = 55² = 3025.

The sum of the squares of the first ten natural numbers is 1² + 2² + ... + 10² = 385.

Hence the difference between the square of the sum of the first ten natural numbers and the sum of the squares of the first ten natural numbers is 3025 - 385 = 2640.

Go through the setup instructions for JavaScript to install the necessary dependencies:

http://exercism.io/languages/javascript/installation

The provided test suite uses Jasmine. You can install it by opening a terminal window and running the following command:

```
npm install -g jasmine
```

Run the test suite from the exercise directory with:

```
jasmine difference-of-squares.spec.js
```

In many test suites all but the first test have been marked "pending".
Once you get a test passing, activate the next one by changing `xit`

to `it`

.

Problem 6 at Project Euler http://projecteuler.net/problem=6

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

```
var Squares = require('./difference-of-squares');
describe('Squares', function () {
describe('up to 5', function () {
var squares = new Squares(5);
it('gets the square of sums', function () {
expect(squares.squareOfSums).toBe(225);
});
xit('gets the sum of squares', function () {
expect(squares.sumOfSquares).toBe(55);
});
xit('gets the difference', function () {
expect(squares.difference).toBe(170);
});
});
describe('up to 10', function () {
var squares = new Squares(10);
xit('gets the square of sums', function () {
expect(squares.squareOfSums).toBe(3025);
});
xit('gets the sum of squares', function () {
expect(squares.sumOfSquares).toBe(385);
});
xit('gets the difference', function () {
expect(squares.difference).toBe(2640);
});
});
describe('up to 100', function () {
var squares = new Squares(100);
xit('gets the square of sums', function () {
expect(squares.squareOfSums).toBe(25502500);
});
xit('gets the sum of squares', function () {
expect(squares.sumOfSquares).toBe(338350);
});
xit('gets the difference', function () {
expect(squares.difference).toBe(25164150);
});
});
});
```

```
function Squares(num){
this.squareOfSums=0;
this.sumOfSquares=0;
for (var x=1; x<=num; ++x) {
this.squareOfSums += x;
this.sumOfSquares += x*x;
}
this.squareOfSums *= this.squareOfSums;
this.difference = Math.abs(this.squareOfSums - this.sumOfSquares);
}
module.exports=Squares;
```

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

- What compromises have been made?
- Are there new concepts here that you could read more about to improve your understanding?

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