I've built a calculator. I would not use angular or bootstrap because I am becoming addicted to them. I also wanted to check for double '.' use, and to limit the screens max text length but did not make it in time.I am new to JavaScript, CSS and HTML and would like to know how I am doing. <html>    <body style=font-size: 40px;  ><div style= max-width: 350px; class=bordered><div class=cont bordered> <label style=max-width:340px;  id=screen>welcome!</label> </div>    <div class=cont>        <button class=bt onclick=code(7)>7</button>        <button class=bt onclick=code(8)>8</button>        <button class=bt onclick=code(9)>9</button>        <button class=bt style=margin-left: 50px;  onclick=code('+')>+</button>        <button class=bt onclick=code('-')>-</button><button class=bt onclick=clr()>C</button>        </div><div class=cont>        <button class=bt onclick=code(4)>4</button>        <button class=bt onclick=code(5)>5</button>        <button class=bt onclick=code(6)>6</button>        <button class=bt style=margin-left: 50px;  onclick=code('*')>*</button>        <button class=bt onclick=code('/')>/</button>        </div><div class=cont>        <button class=bt onclick=code(1)>1</button>        <button class=bt onclick=code(2)>2</button>        <button class=bt onclick=code(3)>3</button>        <button class=bt style=margin-left: 50px;  onclick=code('%')>%</button>        <button class=bt onclick=code('(')>(</button>        <button class=bt onclick=code(')')>)</button>    </div><div class=cont>    <button class=bt onclick=code(0) style= padding-right: 25px; padding-left: 25px;> 0 </button>        <button class=bt style=; margin-left:2px; padding:0 10px 0 10px; onclick=code('.')>,</button>    <button class=bt onclick=compiler() style= padding-right: 30px; padding-left: 30px; margin-left: 50px;> = </button></div></div></body><script >    //regular expression for input controll and users value holder.var rg = new RegExp(/\d/);var codestr = ;//event listener for button presses and input controllvar code = function(str){    var tested = rg.test(codestr.substring(codestr.length-1));    var sstring = (codestr.substring(codestr.length-1));    (str==. && !tested ?         codestr = codestr+0+str : ((rg.test(str) || str==( || str==)) ?             codestr = codestr+str : (tested || sstring==( || sstring==)) ?             codestr= codestr+str: restring(str) )) ;    document.getElementById('screen').innerHTML = codestr;};function restring(str){ codestr = (codestr.substring(0,codestr.length -1))+str };//user input interpreter ( calculator logic )var compiler = function(){     var rezPlz = new Function('return '+codestr)();     codestr = +rezPlz;    document.getElementById('screen').innerHTML = codestr;};//clear buttonfunction clr(){codestr=;    document.getElementById('screen').innerHTML = 0;}</script></html><style rel=stylesheet type=text/css>button{    font-size:40px;    background-color: #FAFAFA;}.cont{    margin: 5px;    padding-top:6px    }.bt{    display: inline;    padding: 0 5px 0 5px;    margin-top: 0px;    border: solid;    border-width: 1px;    border-color: blue;    }.bt:hover{    background-color: darkblue;    color:#F0F0F0;      }.bordered{        border:solid;         border-width: 2px;         border-color : blue;         outline:solid;         outline-width:1px;         outline-color:aqua;    }</style>I know it's not mobile friendly, but that's what I get for doing a no-bootstrap project in short time.
Basic web calculator
javascript;html;css;calculator