贡献保证金百分比

Question

我已经制定了一个计算产品贡献边际的公式，就是百分比限制在100％。

如果我们以0.2欧元的价格购买产品并以99欧元的价格出售，基本上我们的收入会超过100％。

$("#tb_calculator").change(function(){
$this = $(this);
var price_in = $this.find(".tb_price_in").val().replace(',', '.');
var price_out = $this.find(".tb_price_out").val().replace(',', '.');
var quantity = $this.find(".tb_quantity").val().replace(',', '.');

//var percentage = (price_out / price_in - 1)*100;
var percentage = (price_in / price_out);
var tb_value = (price_out*quantity - price_in*quantity);

//console.log(percentage);
var final_percentage = Math.round(((1-percentage)*100));
if (final_percentage === Infinity || final_percentage === "" || isNaN(final_percentage) || final_percentage < 0 || percentage < 0) {
  var final_percentage = 0;
}
if (tb_value === Infinity || tb_value === "" || isNaN(tb_value)) {
  var tb_value = 0;
}

function tofixed(val)
{
   return parseFloat(val.toFixed(2));
}

$(".tb_count").val(tofixed(tb_value)+"kr - ("+final_percentage+"%)");
});

jsFiddle