Need help with Calculator

JavaScript
1

Hello,
I´m making a calculator and i´m almost done. But need help with +/- button and divide by zero problem. So if there is someone who can help and get this problem done i would be thankful.
Also i found a problem with my “.” button because you cant press it after every number clicked and i need to be clicked only once per one number if you get me no like 7,2,3 but only 7,23 then normal operator + and again only once 7,23.
Here is my code so far. Since i cant upload links yet here it is in messy form…
Html is on picture because it wont show there sorry.

a
a939×913 93.3 KB

function getHistory(){
return document.getElementById(“history-value”).innerText;
}

function printHistory(num){
document.getElementById(“history-value”).innerText=num;
}

function getOutput(){
return document.getElementById(“output-value”).innerText;
}

function printOutput(num){
if(num==""){
document.getElementById(“output-value”).innerText=num;
}
else{
document.getElementById(“output-value”).innerText=getFormattedNumber(num);
}
}

function getFormattedNumber(num){
var n = Number(num);
var value = n.toLocaleString(“en”);
return value;
}

function reverseNumberFormat(num){
return Number(num.replace(/,/g,’’));
}

var operator = document.getElementsByClassName(“operator”);
for(var i =0;i<operator.length;i++){
operator[i].addEventListener(‘click’,function(){
if(this.id==“clear”){
printHistory("");
printOutput("");
}
else if(this.id==“backspace”){
var output=reverseNumberFormat(getOutput()).toString();
if(output){
output= output.substr(0,output.length-1);
printOutput(output);
}
}
else{
var output=getOutput();
var history=getHistory();
if(output==""&&history!=""){
if(isNaN(history[history.length-1])){
history= history.substr(0,history.length-1);
}
}
if(output!="" || history!=""){
output= output==""?output:reverseNumberFormat(output);
history=history+output;
if(this.id=="="){
var result=eval(history);
printOutput(result);
printHistory("");
}
else{
history=history+this.id;
printHistory(history);
printOutput("");
}
}
}
});
}

var number = document.getElementsByClassName(“number”);
for(var i =0;i<number.length;i++){
number[i].addEventListener(‘click’,function(){
var output=reverseNumberFormat(getOutput());
if(output!=NaN){
output=output+this.id;
printOutput(output);
}
});
}