<select class="form-control input-lg" size="1" name="tipe" id="tipe">
					<option value="" disabled selected>Tipe Barang</option>
					<option value="10000">Barang</option>
					<option value="11000">Motor</option>
					<option value="12000">Hewan</option>
					<option value="15000">Dokumen</option>
				</select>

<input type="hidden" name="toppings_tot" value="0" />

				<input type="number" class="form-control" name="tarif" id="tarif" value="0" readonly="readonly" disabled required />
				<span id="tarif"></span>

<script type="text/javascript">
	// functions assigned to onchange properties
	document.getElementById('tipe').onchange = function() {
		// access form and value properties via this (keyword)
		var form = this.form;
		var tarif = parseFloat( this.value ) + parseFloat( form.elements['toppings_tot'].value );
		form.elements['tarif'].value = formatDecimal(tarif);
	};

	document.getElementById('toppings').onchange = function() {
		var form = this.form;
		form.elements['toppings_tot'].value = 0; // reset toppings total

		// getSelectedOptions function handles select-multiple
		// pass select list (this) and callback function
		getSelectedOptions( this, calcToppingsTotal );

		// add toppings total and size price to get total
		var tops_tot = parseFloat( form.elements['toppings_tot'].value );
		var size_price = parseFloat( form.elements['tipe'].value );
		form.elements['tarif'].value = formatDecimal(tops_tot + size_price );
	};

	// called for each selected option, adding its value to toppings total
	function calcToppingsTotal(opt) {
		// get reference to hidden toppings total field
		var tot_fld = opt.form.elements['toppings_tot'];
		var val = parseFloat( tot_fld.value );
		// add value of opt to total
		tot_fld.value = val + parseFloat( opt.value );
	}

	// handles selected options in a select-multiple
	function getSelectedOptions(sel, fn) {
		var opts = [], opt;

		for (var i=0, len=sel.options.length; i<len; i++) {
			opt = sel.options[i];
			if ( opt.selected ) {
				opts.push(opt);
				if (fn) {
					fn(opt);
				}
			}
		}
		return opts;
	}

	// format val to n number of decimal places
	// modified version of Danny Goodman's (JS Bible)
	function formatDecimal(val, n) {
		n = n || 2;
		var str = "" + Math.round ( parseFloat(val) * Math.pow(10, n) );
		while (str.length <= n) {
			str = "0" + str;
		}
		var pt = str.length - n;
		return str.slice(0,pt) + "." + str.slice(pt);
	}</script>