feat(vector2): add initial Vector2 implementation (#57)

* feat(vector2): add initial Vector2 implementation
* feat(vector2): add accessors for x, y
* chore: add test for setElements
* chore: add additional tests

src/lib/Vector2.mjs

@@ -0,0 +1,196 @@
+import { EPSILON } from './common.mjs';
+
+/**
+ * Default values
+ *
+ * @readonly
+ * @memberof Vector2
+ * @type {Array}
+ */
+const DEFAULT = [0.0, 0.0];
+
+Object.freeze(DEFAULT);
+
+/**
+ * Element length
+ *
+ * @readonly
+ * @memberof Vector2
+ * @type {Number}
+ */
+const LENGTH = 2;
+
+/**
+ * A 2-component vector.
+ *
+ * @extends Float32Array
+ */
+class Vector2 extends Float32Array {
+  /**
+   * Create a new vector.
+   *
+   * @param {...*} args Arguments for new vector
+   */
+  constructor(...args) {
+    if (args.length === 0) {
+      super(DEFAULT);
+    } else {
+      super(...args);
+    }
+
+    if (this.length !== LENGTH) {
+      throw new Error('Invalid length');
+    }
+  }
+
+  /**
+   * @type {Number}
+   */
+  get x() {
+    return this[0];
+  }
+
+  set x(x) {
+    this[0] = x;
+  }
+
+  /**
+   * @type {Number}
+   */
+  get y() {
+    return this[1];
+  }
+
+  set y(y) {
+    this[1] = y;
+  }
+
+  /**
+   * Check for approximate equality against the given vector using given
+   * epsilon.
+   *
+   * @param {Vector2} v Vector to compare
+   * @param {Number} e Epsilon
+   * @returns {Boolean} Approximate equality
+   */
+  approximates(v, e = EPSILON) {
+    const t0 = this[0], t1 = this[1];
+    const v0 = v[0],    v1 = v[1];
+
+    return Math.abs(t0 - v0) <= e * Math.max(1.0, Math.abs(t0), Math.abs(v0)) &&
+           Math.abs(t1 - v1) <= e * Math.max(1.0, Math.abs(t1), Math.abs(v1));
+  }
+
+  /**
+   * Check for exact equality against the given vector.
+   *
+   * @param {Vector2} v Vector to compare
+   * @returns {Boolean} Equality
+   */
+  equals(v) {
+    return this[0] === v[0] && this[1] === v[1];
+  }
+
+  /**
+   * Set the elements of this vector to the given values.
+   *
+   * @param {Number} x X component
+   * @param {Number} y Y component
+   * @returns {Vector2} Self
+   */
+  setElements(x, y) {
+    this[0] = x;
+    this[1] = y;
+
+    return this;
+  }
+
+  /**
+   * Execute the provided function once for each vector in the given array.
+   *
+   * @param {(Float32Array|Array)} arr Array to traverse
+   * @param {Function} cb Callback
+   * @returns {void}
+   */
+  static forEach(arr, cb) {
+    if (arr.length % LENGTH !== 0) {
+      throw new Error('Invalid length');
+    }
+
+    const l = arr.length;
+    const v = new Vector2();
+
+    for (let i = 0; i < l; i += LENGTH) {
+      v[0] = arr[i];
+      v[1] = arr[i + 1];
+
+      cb.call(this, v, i / LENGTH, arr);
+
+      arr[i] = v[0];
+      arr[i + 1] = v[1];
+    }
+  }
+
+  /**
+   * Generate an iterator capable of iterating over an array as vector indices.
+   *
+   * @param {(Float32Array|Array)} arr Array to iterate
+   * @returns {Iterator} New iterator
+   */
+  static *keys(arr) {
+    if (arr.length % LENGTH !== 0) {
+      throw new Error('Invalid length');
+    }
+
+    const l = arr.length / LENGTH;
+
+    for (let i = 0; i < l; i++) {
+      yield i;
+    }
+  }
+
+  /**
+   * Create a new vector with a variable number of arguments.
+   *
+   * @param {...*} args Arguments for new vector
+   * @returns {Vector2} New vector
+   */
+  static of(...args) {
+    if (args.length === 0) {
+      return new Vector2();
+    } else {
+      return new Vector2(args);
+    }
+  }
+
+  /**
+   * Generate an iterator capable of iterating over an array as vectors.
+   *
+   * @param {(Float32Array|Array)} arr Array to iterate
+   * @returns {Iterator} New iterator
+   */
+  static *values(arr) {
+    if (arr.length % LENGTH !== 0) {
+      throw new Error('Invalid length');
+    }
+
+    const l = arr.length;
+    const v = new Vector2();
+
+    for (let i = 0; i < l; i += LENGTH) {
+      v[0] = arr[i];
+      v[1] = arr[i + 1];
+
+      yield v;
+
+      arr[i] = v[0];
+      arr[i + 1] = v[1];
+    }
+  }
+}
+
+Vector2.DEFAULT = DEFAULT;
+
+Vector2.LENGTH = LENGTH;
+
+export default Vector2;

src/lib/index.mjs

@@ -3,6 +3,7 @@ import Matrix3 from './Matrix3.mjs';
 import Matrix4 from './Matrix4.mjs';
 import Plane from './Plane.mjs';
 import Quaternion from './Quaternion.mjs';
+import Vector2 from './Vector2.mjs';
 import Vector3 from './Vector3.mjs';
 
 export {
@@ -12,5 +13,6 @@ export {
   Matrix4,
   Plane,
   Quaternion,
+  Vector2,
   Vector3,
 };