is this a triangle

Author: nerdrun

is_this_a_triangle/main.js

@@ -0,0 +1,23 @@
+function isTriangle(a,b,c) {
+  /// a mathmatical way
+  return a + b > c && a + c > b && c + b > a;
+
+  /// deconstructing assignment (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment)
+  [a, b, c] = [a, b, c].sort((x, y) => x-y);
+  return a + b > c;
+
+  if(a <= 0 || b <= 0 || c <= 0) return false;
+
+  /// ES6
+  const array = [a, b, c].sort((a, b) => a - b);
+  return array.pop() < array.reduce((acc, cur) => acc + cur, 0);
+
+  /// Simple way
+  let biggest = a;
+  let twoSides = b + c;
+  if(biggest < b) biggest = b, twoSides = a + c;
+  if(biggest < c) biggest = c, twoSides = a + b;
+  return biggest < twoSides;
+}
+
+module.exports = isTriangle;

is_this_a_triangle/main.test.js

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+const isTriangle = require('./main');
+
+describe('negative test', () => {
+  test('-1, 1, 1 returns false', () => {
+    expect(isTriangle(-1, 1, 1)).toBe(false);
+  });
+  test('1, 2, 2 returns true', () => {
+    expect(isTriangle(1, 2, 2)).toBe(true);
+  });
+});
+
+describe('find the biggest number', () => {
+  test('3, 2, 2 returns true', () => {
+    expect(isTriangle(3, 2, 2)).toBe(true);
+  });
+  test('7, 5, 1 returns false', () => {
+    expect(isTriangle(7, 5, 1)).toBe(false);
+  });
+  test('2, 4, 6 returns false', () => {
+    expect(isTriangle(2, 4, 6)).toBe(false);
+  });
+  test('10, 1, 8 returns false', () => {
+    expect(isTriangle(10, 1, 8)).toBe(false);
+  });
+});