get closest point on line with specific point

closestXY.js

function closestXY(x0,y0,x1,y1, mx, my) {

    var dx = x1 - x0;
    var dy = y1 - y0;

    var t = ((mx - x0) * dx + (my - y0) * dy) / (dx * dx + dy * dy);
    t = Math.max(0, Math.min(1, t));

    var x = lerp(x0, x1, t);
    var y = lerp(y0, y1, t);

    return ({x: x, y: y});
}

function lerp(value1, value2, amount) {
    amount = amount < 0 ? 0 : amount;
    amount = amount > 1 ? 1 : amount;
    return value1 + (value2 - value1) * amount;
}