How to operate with more than 2 numbers [duplicate]

I’m trying to build a calculator with HTML, CSS and JS but I can’t fix how to operate for example 1 + 2 + 3. Right now I’m getting 5 as a result with my actual code and the correct result should be 6. Here you have all my JS. Hope someone can help me. If you need the HTML let me know!

I want to operate with more than 2 numbers.

let operacion1;
let operacion2;
let performance;

const iniciamosCalculadoraPRO = () => {
  let resultado = document.getElementById("resultado");
  let reset = document.getElementById("reset");
  let suma = document.getElementById("suma");
  let minus = document.getElementById("minus");
  let multi = document.getElementById("multi");
  let divi = document.getElementById("divi");
  let equal = document.getElementById("equal");
  let root = document.getElementById("root");
  let one = document.getElementById("one");
  let two = document.getElementById("two");
  let three = document.getElementById("three");
  let four = document.getElementById("four");
  let five = document.getElementById("five");
  let six = document.getElementById("six");
  let seven = document.getElementById("seven");
  let eight = document.getElementById("eight");
  let nine = document.getElementById("nine");
  let cero = document.getElementById("cero");
};


one.onclick = function() {
  resultado.textContent = resultado.textContent + "1";
};
two.onclick = function() {
  resultado.textContent = resultado.textContent + "2";
};
three.onclick = function() {
  resultado.textContent = resultado.textContent + "3";
};
four.onclick = function() {
  resultado.textContent = resultado.textContent + "4";
};
five.onclick = function() {
  resultado.textContent = resultado.textContent + "5";
};
six.onclick = function() {
  resultado.textContent = resultado.textContent + "6";
};
seven.onclick = function() {
  resultado.textContent = resultado.textContent + "7";
};
eight.onclick = function() {
  resultado.textContent = resultado.textContent + "8";
};
nine.onclick = function() {
  resultado.textContent = resultado.textContent + "9";
};
cero.onclick = function() {
  resultado.textContent = resultado.textContent + "0";
};
reset.onclick = function() {
  resCalculator();
};
suma.onclick = function() {
  operacion1 = resultado.textContent;
  performance = "+";
  clearAll();
};
minus.onclick = function() {
  operacion1 = resultado.textContent;
  performance = "-";
  clearAll();
};
multi.onclick = function() {
  operacion1 = resultado.textContent;
  performance = "*";
  clearAll();
};
divi.onclick = function() {
  operacion1 = resultado.textContent;
  performance = "/";
  clearAll();
};
equal.onclick = function() {
  operacion2 = resultado.textContent;
  showingResults();
};

root.onclick = function() {
  operacion1 = resultado.textContent;
  rootOperation();
}

punto.onclick = function() {
  if (!resultado.textContent.includes(".")) {
    resultado.textContent = resultado.textContent + ".";
  }
}




const clearAll = () => {
  resultado.textContent = "";
}

const resCalculator = () => {
  resultado.textContent = "";
  operacion1 = 0;
  operacion2 = 0;
  performance = "";
}

const rootOperation = () => {
  resultado.textContent = Math.sqrt(operacion1).toFixed(3);
}



const showingResults = () => {
  let resultadosGlobales = 0;
  switch (performance) {
    case "+":
      resultadosGlobales = parseFloat(operacion1) + parseFloat(operacion2);
      break;

    case "-":
      resultadosGlobales = parseFloat(operacion1) - parseFloat(operacion2);
      break;

    case "*":
      resultadosGlobales = parseFloat(operacion1) * parseFloat(operacion2);
      break;

    case "/":
      resultadosGlobales = parseFloat(operacion1) / parseFloat(operacion2);
      break;
  }
  resCalculator();
  resultado.textContent = resultadosGlobales;
}