javascript - rails : displaying a value dynamically calculated in my form

Question

在我的 new.html.erb 中，我有以下内容:

<%= hidden_field :shipping_charges %>
<%= label_tag :rush_shipment, "Rush My Shipment" %>>
<%= check_box_tag :rush_shipment, :checked => false, :onclick => "add_rush_shipment_charges()" %>

    <p>My Shipping charges: <span id="shipping_charges"></span> 

在我的 javascript 文件中，我有以下内容:

function add_rush_shipment_charges()
{
    document.getElementById('shipping_charges').value = 25;
}

当我单击该复选框时，我应该会看到 25 显示在运费之后，但什么也没有发生。任何想法。

编辑:

请注意，我编辑了问题以反射(reflect)我从答案 #1 中获得的信息，但我仍然没有看到任何东西。

Answer 1

Where you want to show the shipping charges? Lets assume your view is like:
<%= hidden_field :shipping_charges %>
<%= label_tag :rush_shipment, "Rush My Shipment" %>>
<%= check_box_tag :rush_shipment, :checked => false, :onclick => "add_rush_shipment_charges()" %>
<h3> You shipping charges are: <span id="total_shipping"></span</h1>

现在，在计算完总运费后，您只需更新跨度

function calculate_total_costs(){
  //cost calculation logics
  document.getElementById('total_shipping').value = TOTAL_COSTS
}

现在，在需要时调用函数 calculate_total_costs()!