JavaScript calcalator

The code below shows how to make a simple calculator with JavaScript.

<html>
    <head>
        <title>My app</title>
    </head>
    <body>
        <div style="width:173px; background:lightblue">
            <form name="form">
                <input name="result"/></br></br>
                <input type="button" name="1" value="1" onClick="run('1')" style="width:40px"/>
                <input type="button" name="2" value="2" onClick="run('2')" style="width:40px"/>
                <input type="button" name="3" value="3" onClick="run('3')" style="width:40px"/>
                <input type="button" name="plus" value="+" onClick="runplus()" style="width:40px"/>
                </br>
                <input type="button" name="4" value="4" onClick="run('4')" style="width:40px"/>
                <input type="button" name="5" value="5" onClick="run('5')" style="width:40px"/>
                <input type="button" name="6" value="6" onClick="run('6')" style="width:40px"/>
                <input type="button" name="minus" value="-" onClick="runminus()" style="width:40px"/>
                </br>
                <input type="button" name="7" value="7" onClick="run('7')" style="width:40px"/>
                <input type="button" name="8" value="8" onClick="run('8')" style="width:40px"/>
                <input type="button" name="9" value="9" onClick="run('9')" style="width:40px"/>
                <input type="button" name="divide" value="/" onClick="rundivide()" style="width:40px"/>
                </br>
                <input type="button" name="0" value="0" onClick="run('0')" style="width:40px"/>
                <input type="button" name="." value="." onClick="runpoint()" style="width:40px"/>
                <input type="button" name="%" value="%" onClick="runpercent()" style="width:40px"/>
                <input type="button" name="multiply" value="x" onClick="runmultiply()" style="width:40px"/>
                </br>
                <input type="button" name="clear" value="C" onClick="runclear()" style="width:84px"/>
                <input type="button" name="calc" value="=" onClick="calculate()" style="width:84px"/>
                </br>
            </form>
        </div>
        <script>
            function run(number){
                document.form.result.value += number;
            }
            function runplus(){
                document.form.result.value += '+';
            }
            function runminus(){
                document.form.result.value += '-';
            }
            function runmultiply(){
                document.form.result.value += '*';
            }
            function rundivide(){
                document.form.result.value += '/';
            }
            function runpoint(){
                document.form.result.value += '.';
            }
            function runclear(){
                document.form.result.value = '';
            }
            function runpercent(){
                document.form.result.value += '*(100/1)';
            }
            function calculate(){
                var answer = eval(document.form.result.value);
                document.form.result.value = answer;
            }
        </script>
    </body>
</html>