Operating symbols not appear in javascript calculator

Building a calculator in JavaScript and can’t get the operating symbols to appear or to function in the output line. It works perfectly in Komodo but not in Chrome or Safari. Here is the code:

    <form name="formname">
        <p><input type="number" id="out"></p>
        <p>
            <button type="button" onclick="formname.out.value = formname.out.value + '1';">1</button>
            <button type="button" onclick="formname.out.value = formname.out.value + '2';">2</button>
            <button type="button" onclick="formname.out.value = formname.out.value + '3';">3</button>
            <button type="button" onclick="formname.out.value = formname.out.value + '+';">+</button>
        </p>
        <p>
            <button type="button" onclick="formname.out.value = formname.out.value +'4';">4</button>
            <button type="button" onclick="formname.out.value = formname.out.value +'5';">5</button>
            <button type="button" onclick="formname.out.value = formname.out.value +'6';">6</button>
            <button type="button" onclick="formname.out.value = formname.out.value + '-';">-</button>
        </p>
        <p>
            <button type="button" onclick="formname.out.value = formname.out.value + '7';">7</button>
            <button type="button" onclick="formname.out.value = formname.out.value + '8';">8</button>
            <button type="button" onclick="formname.out.value = formname.out.value + '9';">9</button>
            <button type="button" onclick="formname.out.value = formname.out.value + '*';">*</button>
        </p>
        <p>
            <button type="button" onclick="formname.out.value = '';">c</button>
            <button type="button" onclick="formname.out.value = formname.out.value + '0';">0</button>
            <button type="button" onclick="formname.out.value = formname.out.value = eval(formname.out.value);">=</button>
            <button type="button" onclick="formname.out.value = formname.out.value + '/';">/</button>
        </p>
    </form>