I need help to fix this js$.$ I created the calculator, but the js file doesnt complete. The input only take $1$ digit, so whenever I click more than $1$ digit, it doesnt save the first digit.

let buffer $="0"$;

let runningTotal $=0$;

let previousOperator $=$null;

const screen $=$ document.querySelector$(\text{'}.$screen'$)$;

function buttonClick$($value$)\{$

console.log$($value$)$;

$//$NaN is not a number

if $($isNaN$($parseInt$($value$)))\{$

handleSymbol$($value$)$;

$\}$ else $\{$

handleNumber$($value$)$;

$\}$

rerender$()$;

$\}$

function handleNumber$($number$)\{$

if $($buffer $==="0")\{$

buffer $=$ number;

$\}$ else $\{$

buffer $==$ buffer $+$ number;

$\}$

$\}$

function handleMath$($value$)\{$

if$($buffer $==="0")\{$

$//$do nothing

return;

$\}$

const intBuffer $=$ parseInt$($buffer$)$;

if $($runningTotal $===0)\{$

runningTotal $=$ intBuffer;

$\}$ else $\{$

flushOperation$($intBuffer$)$;

$\}$

previousOperator $=$ value;

buffer $="0"$;

$\}$

function flushOperation$($intBuffer$)\{$

if $($previousOperator $===\text{'}+\text{'})\{$

runningTotal $=$ runningTotal $+$ intBuffer;

$\}$ else if $($previousOperator $===\text{'}-\text{'})\{$

runningTotal $=$ runningTotal $-$ intBuffer;

$\}$ else if $($previousOperator $===\text{'}$x$\text{'})\{$

runningTotal $=$ runningTotal $*$ intBuffer;

$\}$ else $\{$

runningTotal $=$ runningTotal $/$ intBuffer;

$\}$

$\}$

function handleSymbol$($symbol$)\{$

$//$if $($symbol $===\text{'}$AC$\text{'})$

switch $($symbol$)\{$

case $\text{'}$AC$\text{'}$:

buffer $=\text{'}0\text{'}$;

break;

case $\text{'}=\text{'}$:

if$($previousOperator $===$ null$)\{$

return;

$\}$

flushOperation$($parseInt$($buffer$))$;

previousOperator $=$ null;

buffer $=""+$ runningTotal;

runningTotal $=0$;

break;

case 'Del':

if$($buffer$.$length $===1)\{$

buffer $=\text{'}0\text{'}$;

$\}$ else $\{$

buffer $=$ buffer.substring$(0,$ buffer.length $-1)$;

$\}$

break;

case $\text{'}+\text{'}$:

case $\text{'}-\text{'}$:

case $\text{'}/\text{'}$:

case $\text{'}$x$\text{'}$:

handleMath$($symbol$)$;

break;

$\}$

$\}$

function init$()\{$

document.querySelector$(\text{'}.$calc$-$buttons'$)$

$.$addEventListener$("$click$",$ function$($event$)\{$

buttonClick$($event$.$target.innerText$)$;

$\})$

$\}$

function rerender$()\{$

screen.innerText $=$ buffer;

$\}$

document.getElementsByClassName$("$calc$-$button"$)$;

const buttons $=$ document.getElementsByClassName$("$calc$-$button"$)$;

buttonList $=$ Array.prototype.slice.call$($buttons$)$;

buttonList.forEach$(($button$)=>$ button.addEventListener$("$click$",($event$)=>$ buttonClick$($event$.$target.textContent$)))$;$-------$