so basically I want the user to be able to kinda select multiple elements by just drawing over them instead of choosing each manually. what I tried to do was on each element I have this onMouseMove function, and inside that function I am using this:

document.body.onmousedown = function() {
  //Selecting the items here, only if the mouse is also down
}

but it doesnt seem to be working as on mousedown is only true the moment it is clicked. sorry if this has been answered before I tried searching I couldnt find it. Thank you all in advance.