How to find coordinates of a point where 2 points and distance are given with Javascript

Question

I have the coordinates of 2 points A1 (x1,y1) and A2 (x2,y2) and a distance d. I need to find the coordinates of point A3 that is the distance d from point A2 on the linear graph defined by A1 and A2. How can i do that with JavaScript? similar to https://softwareengineering.stackexchange.com/questions/179389/find-the-new-coordinates-using-a-starting-point-a-distance-and-an-angle where the angle is known

Answer 1

var A1 = {
    x : 2,
    y : 2
};

var A2 = {
    x : 4,
    y : 4
};

// Distance
var  d= 2;

// Find Slope of the line
var slope = (A2.y-A1.y)/(A2.x-A1.x);

// Find angle of line
var theta = Math.atan(slope);

// the coordinates of the A3 Point
var A3x= A2.x + d * Math.cos(theta);
var A3y= A2.y + d * Math.sin(theta);

console.log(A3x);
console.log(A3y);