SOURCE

let bt = document.getElementsByTagName("button");
var inpus = document.getElementById("inputs");
var ins = bt.length;
var adds = '', a, b, cc, dd, ee;//前面数值 后面数值 计算符号 临时数据 显示数据
for (let i = 0; i < ins; i++) {
    let das = bt[i];
    das.addEventListener("click", () => {
        runn(das.innerHTML);
    });
}

function show(bb) {
    inpus.value = bb;
}

function jisuan(a, b, c) {
    adds += abc;
    return adds;
}

function runn(e) {
    if (e >= 0 && e <= 9 || e == ".") {
        ee += e;
        show(ee);
    } else if (e == "+" || e == "-" || e == "*" || e == "/") {
        cc = "+";
        a=ee;

        
        a += dd;
    }


    if (e == "") {
        switch (e) {
            case "del":
                adds = '';
                show(adds);
                break;
            case "c":
                break;
                show(jisuan());
                break;
            case "+":

                break;
            case "-":
                cc = "-";
                b += adds;

                break;
            case "*":
                cc = "*";
                b += adds;
                break;
            case "/":
                cc = "/";
                b += adds;
                break;
            default: {

            }

        }
    }




}

<div class="back">
	<div class="inputs">
		<input id="inputs">
</div>

<div class="ak">
  <button id="as">del</button> 
   <button id="ass">c</button>
</div>

<div>
  <button>7</button>
   <button>8</button>
     <button>9</button>
   <button>=</button>
</div>
<div>
 <button>4</button>
   <button>5</button>
     <button>6</button>
   <button>+</button>
</div>
<div>
   <button>1</button>
   <button>2</button>
     <button>3</button>
   <button>-</button>
</div>
<div>
 <button>*</button>
   <button>0</button>
     <button>.</button>
   <button>/</button>
</div>
</div>

#back {
    width: 600px;
    height: 600px;
}

#inputs {
    width: 46.5%;
}

button {
    width: 60px;
}

#ak {
    width: 1300px;
}

#as {
    width: 27%;
}

#ass {
    width: 20%;
}