Can´t get Javascript to remove css property : I'm trying to make a loading screen for my project. I need the javascript to remove the CSS property "Display: none" from (page) I can't figure out why my code doesn't work. I'm very new to javascript so don't get mad if this is a simple question.  
hope you can

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

    window.onload(loader)

    function loader(){
        document.getElementById("page").style.removeProperty("display");
    }


<!-- language: lang-css -->

    #page{
        display: none;
    }


    /* Loading */
    #loading{
        width: 100%;
        height:100vh;
        background-color: #428BCA;
    }

    .loading_container{
        margin: 0;
        position: absolute;
        top: 50%;
        left: 50%;
        margin-right: -50%;
        transform: translate(-50%, -50%);
    }

    #spin {
    border: 16px solid #f3f3f3; /* Light grey */
        border-top: 16px solid #3498db; /* Blue */
        border-radius: 50%;
        width: 120px;
        height: 120px;
        animation: spin 2s linear infinite;
    }

    @keyframes spin {
        0% { transform: rotate(0deg); }
        100% { transform: rotate(360deg); }
    }

    #loading h1{
        color: #FFF;
        margin-left:10px; 
    }

<!-- language: lang-html -->

    <div id="page">

    Content!

    </div>
    <div id="loading">
      <div class="loading_container">
      <div id="spin"></div>
      <h1>Loading...</h1>
    </div>
    </div>


<!-- end snippet -->

 help.  