function solve() {
    let keys=Array.from(document.getElementsByClassName('keys'));
    let exprOutput=document.getElementById('expressionOutput');
    let result=document.getElementById('resultOutput');
    let clearBtn=document.querySelector('.clear');
    let operand;
    let firstNum='';
    let secondNum='';

    let calculator={
        '+':(a,b)=>a+b,
        '-':(a,b)=>a-b,
        '*':(a,b)=>a*b,
        '/':(a,b)=>a/b,
    }
    keys.map(key=>key.addEventListener('click', function (evt) {
        let currSelection=evt.target.value;

        clearBtn.addEventListener('click',()=>{
            exprOutput.textContent='';
            result.textContent='';
            firstNum='';
            secondNum='';
            operand='';
        });
        if(Number(currSelection)||currSelection==="."||currSelection==='0'){
            if(!operand){
                firstNum+=currSelection;
                exprOutput.textContent+=currSelection;
            }else {
                secondNum+=currSelection;
                exprOutput.textContent+=currSelection
            }
        }else if(calculator.hasOwnProperty(currSelection)){
            operand=currSelection;
            exprOutput.textContent+=`${operand} `;
        }else if(currSelection==='='){
            if(Number(firstNum) && Number(secondNum)){
                result.textContent=calculator[operand](Number(firstNum),Number(secondNum));
            }else {
                result.textContent='NaN'
            }
        }

    }))



}