Compare three products in table format using if else statements

I am doing a project and we have to compare three items side-by-side in a table with Javascript. I have defined all my values and now I am just having trouble with the if/else statements. What I want to define is that if the first column is empty, then populate it with the first set of data. If there is already data in there, then populate column 2 instead.

Any suggestions regarding format, etc would be appreciated. Here is my current Js:

DOM.compare1[index].onclick = function(){

    if (DOM.compareCell1[index].innerHTML == "..."){ 
    compareColumn1.price.innerHTML = device1.price;
    compareColumn1.brand.innerHTML = device1.brand;
    compareColumn1.screenSize.innerHTML = device1.screenSize;
    compareColumn1.screenSurface.innerHTML = device1.screenSurface;
    compareColumn1.touchScreen.innerHTML = device1.touchScreen;
    compareColumn1.pixels.innerHTML = device1.pixels;
    compareColumn1.storage.innerHTML = device1.storage;
    compareColumn1.ssd.innerHTML = device1.ssd;
    compareColumn1.ram.innerHTML = device1.ram;
    compareColumn1.cpu.innerHTML = device1.cpu;
    compareColumn1.gpu.innerHTML = device1.gpu;
    compareColumn1.weight.innerHTML = device1.weight;
} 

else if ((DOM.compareCell1[index].innerHTML !== "..."){
    compareColumn2.price.innerHTML = device1.price;
    compareColumn2.brand.innerHTML = device1.brand;
    compareColumn2.screenSize.innerHTML = device1.screenSize;
    compareColumn2.screenSurface.innerHTML = device1.screenSurface;
    compareColumn2.touchScreen.innerHTML = device1.touchScreen;
    compareColumn2.pixels.innerHTML = device1.pixels;
    compareColumn2.storage.innerHTML = device1.storage;
    compareColumn2.ssd.innerHTML = device1.ssd;
    compareColumn2.ram.innerHTML = device1.ram;
    compareColumn2.cpu.innerHTML = device1.cpu;
    compareColumn2.gpu.innerHTML = device1.gpu;
    compareColumn2.weight.innerHTML = device1.weight;
}