Personal greeting

[churitos]

Dear all,

My coding experience is not sufficient to get this to work, so I kindly ask for some help. I like to get a personal message above the clock in the header.
There is some space for HTML code, but I like it to be Javascript.
Part in config.js:

{
            type: HEADER_ITEMS.CUSTOM_HTML,
            html: 'welcome',
},

Code I like to inject:

var welcome;  
    var date = new Date();  
    var hour = date.getHours();  
    if (hour < 12) {  
      welcome = "Goedemorgen!";  
    } else if (hour < 18) {  
      welcome = "Goedemiddag!";  
    } else {  
      welcome = "Goedenavond!";  
    }  
    document.write("<h2>" + "<font color='blue'>" + welcome + "</font>" );

Thank you in advance!