A simple lightweight math vector implementation.

Vector.js

/**
 * Represents a math vector with x, y position, direction and magnitude.
 */
class Vector {
    constructor(x, y) {
        this._compute(x, y);
    }
    _compute(x, y) {
        this.x = x;
        this.y = y;
        this.angle = Math.atan2(y, x);
        this.length = Math.sqrt(x * x + y * y);
    }
    /**
     * Sets the angle of the vector with respect to the unit vector.
     * @param angle The angle to unity.
     */
    setAngle(angle) {
        this.angle = angle;
        this.x = Math.cos(this.angle) * this.length;
        this.y = Math.sin(this.angle) * this.length;
    }
    /**
     * Sets the distance to unit vector.
     * @param length The length to the unit vector.
     */
    setLength(length) {
        this.length = length;
        this.x = Math.cos(this.angle) * this.length;
        this.y = Math.sin(this.angle) * this.length;
    }
    /**
     * Add the given vector to the current vector.
     * @param v The vector to add.
     */
    add(v) {
        this._compute(this.x + v.x, this.y + v.y);
    }
    /**
     * Subtracts the given vector to the current vector.
     * @param v The vector to subtract.
     */
    subtract(v) {
        this._compute(this.x - v.x, this.y - v.y);
    }
    /**
     * Multiplies the current vector by a scalar.
     * @param scalar The scalar to multiply.
     */
    multiply(scalar) {
        this._compute(this.x * scalar, this.y * scalar);
    }
    /**
     * Divides the current vector by a scalar.
     * @param scalar The scalar to divide.
     */
    divide(scalar) {
        this._compute(this.x / scalar, this.y / scalar);
    }
    /**
     * Adds two vectors together.
     * @param v1 Vector operand one for addition.
     * @param v2  Vector operand two for addition.
     */
    static add(v1, v2) {
        const x = v1.x + v2.x;
        const y = v1.y + v2.y;
        return new Vector(x, y);
    }
    /**
     * Subtract two vectors.
     * @param v1 Vector operand one for subtraction.
     * @param v2  Vector operand two for subtraction.
     */
    static subtract(v1, v2) {
        const x = v1.x - v2.x;
        const y = v1.y - v2.y;
        return new Vector(x, y);
    }
    /**
     * Multiplies a vector and a scalar.
     * @param v1 Vector operand for multiplication.
     * @param v2 Scalar operand for multiplication.
     */
    static multiply(v, k) {
        return new Vector(v.x * k, v.y * k);
    }
}