PointsDist.js

var points=[
    {x:0,y:0},
    {x:3.3,y:4.4}
];
points.dist=function()
{
    var deltax=this[0].x-this[1].x;
    var deltay=this[0].y-this[1].y;
    return Math.sqrt(deltax*deltax+deltay*deltay);
};
console.log(points.dist());

"D:\Program Files\JetBrains\WebStorm 8.0.6\bin\runnerw.exe" "C:\Program Files\nodejs\node.exe" PointsDist.js
5.5

Process finished with exit code 0