# Snippet: Normal vector of a line segment

The vector $$\mathbf{v}=\mathbf{B}-\mathbf{A}$$ between two points $$\mathbf{A}$$ and $$\mathbf{B}$$ has two normals, being the negation of each other. Rotating the vector $$\mathbf{v}$$ counterclockwise is the definition of the perp opererator and gives one normal vector:

$\mathbf{v}^\perp = (-v_y, v_x)$

## JavaScript implementation

function normals(A, B) {
var dx = B.x - A.x;
var dy = B.y - A.y;
return [{x: -dy, y: dx}, {x: dy, y: -dx}];
}