calculating the point of intersection of two lines

Question

I have dynamically generated lines that animate and I want to detect when a lines hits another. I\'m trying to implement some basic linear algebra to obtain the equation of

Answer 1

You may do as follows;

function lineIntersect(a,b){
  a.m = (a[0].y-a[1].y)/(a[0].x-a[1].x);  // slope of line 1
  b.m = (b[0].y-b[1].y)/(b[0].x-b[1].x);  // slope of line 2
  return a.m - b.m < Number.EPSILON ? undefined
                                    : { x: (a.m * a[0].x - b.m*b[0].x + b[0].y - a[0].y) / (a.m - b.m),
                                        y: (a.m*b.m*(b[0].x-a[0].x) + b.m*a[0].y - a.m*b[0].y) / (b.m - a.m)};
}

var line1 = [{x:3, y:3},{x:17, y:8}],
    line2 = [{x:7, y:10},{x:11, y:2}];
console.log(lineIntersect(line1, line2));