# rootulp's solution

## to Triangle in the JavaScript Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

#### Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Determine if a triangle is equilateral, isosceles, or scalene.

An equilateral triangle has all three sides the same length.

An isosceles triangle has at least two sides the same length. (It is sometimes specified as having exactly two sides the same length, but for the purposes of this exercise we'll say at least two.)

A scalene triangle has all sides of different lengths.

## Note

For a shape to be a triangle at all, all sides have to be of length > 0, and the sum of the lengths of any two sides must be greater than or equal to the length of the third side. See Triangle Inequality.

## Dig Deeper

The case where the sum of the lengths of two sides equals that of the third is known as a degenerate triangle - it has zero area and looks like a single line. Feel free to add your own code/tests to check for degenerate triangles.

## Setup

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

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

## Running the test suite

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 triangle.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`.

## Source

The Ruby Koans triangle project, parts 1 & 2 http://rubykoans.com

## Submitting Incomplete Solutions

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

### triangle.spec.js

``````var Triangle = require('./triangle');

describe('Triangle', function () {
it('equilateral triangles have equal sides', function () {
var triangle = new Triangle(2, 2, 2);
expect(triangle.kind()).toEqual('equilateral');
});

xit('larger equilateral triangles also have equal sides', function () {
var triangle = new Triangle(10, 10, 10);
expect(triangle.kind()).toEqual('equilateral');
});

xit('isosceles triangles have last two sides equal', function () {
var triangle = new Triangle(3, 4, 4);
expect(triangle.kind()).toEqual('isosceles');
});

xit('isosceles triangles have first two sides equal', function () {
var triangle = new Triangle(2, 2, 3);
expect(triangle.kind()).toEqual('isosceles');
});

xit('isosceles trianges have first and last sides equal', function () {
var triangle = new Triangle(4, 3, 4);
expect(triangle.kind()).toEqual('isosceles');
});

xit('isosceles triangles have two first sides equal', function () {
var triangle = new Triangle(4, 4, 3);
expect(triangle.kind()).toEqual('isosceles');
});

xit('isosceles triangles have in fact exactly two sides equal', function () {
var triangle = new Triangle(10, 10, 2);
expect(triangle.kind()).toEqual('isosceles');
});

xit('scalene triangles have no equal sides', function () {
var triangle = new Triangle(3, 4, 5);
expect(triangle.kind()).toEqual('scalene');
});

xit('scalene triangles have no equal sides at a larger scale too', function () {
var triangle = new Triangle(10, 11, 12);
expect(triangle.kind()).toEqual('scalene');
});

xit('scalene triangles have no equal sides in descending order either', function () {
var triangle = new Triangle(5, 4, 2);
expect(triangle.kind()).toEqual('scalene');
});

xit('very small triangles are legal', function () {
var triangle = new Triangle(0.4, 0.6, 0.3);
expect(triangle.kind()).toEqual('scalene');
});

xit('test triangles with no size are illegal', function () {
var triangle = new Triangle(0, 0, 0);
expect(triangle.kind.bind(triangle)).toThrow();
});

xit('triangles with negative sides are illegal', function () {
var triangle = new Triangle(3, 4, -5);
expect(triangle.kind.bind(triangle)).toThrow();
});

xit('triangles violating triangle inequality are illegal', function () {
var triangle = new Triangle(1, 1, 3);
expect(triangle.kind.bind(triangle)).toThrow();
});

xit('triangles violating triangle inequality are illegal 2', function () {
var triangle = new Triangle(7, 3, 2);
expect(triangle.kind.bind(triangle)).toThrow();
});

xit('triangles violating triangle inequality are illegal 3', function () {
var triangle = new Triangle(10, 1, 3);
expect(triangle.kind.bind(triangle)).toThrow();
});
});``````
``````function Triangle(sideA, sideB, sideC) {
'use strict';

this.kind = function() {
if (this.error()) {
throw Error;
} else if (this.equilateral()) {
return 'equilateral';
} else if (this.isosceles()) {
return 'isosceles';
} else {
return 'scalene';
}
}

this.equilateral = function() {
return sideA === sideB && sideB === sideC
}

this.isosceles = function() {
return sideA === sideB || sideB === sideC || sideA === sideC
}

this.error = function() {
return this.inequality(sideA, sideB, sideC) ||
this.inequality(sideB, sideC, sideA) ||
this.inequality(sideA, sideC, sideB)
}

this.inequality = function(x, y, z) {
return x + y <= z
}
}

module.exports = Triangle``````