如何在运算符之间只允许一位小数（计算器应用）

Question

我一直绞尽脑汁试图弄清楚如何防止算术运算符之间的每个数字超过一个小数。此外，单击按钮而不是循环并添加事件侦听器时，使用事件委派会更节省内存吗？任何帮助将不胜感激。

const display = document.querySelector(".result");
const number = document.getElementsByClassName("number-button");
const operator = document.getElementsByClassName("operator-button");
const equals = document.querySelector(".equals-button");
const clear = document.querySelector(".all-clear");
const backSpace = document.querySelector(".backspace");
let state = 0;

function reset() {
  display.value = "";
}

// Iterates through number elements and sets event listeners
for (var i = 0; i < number.length; i++) {
  number[i].addEventListener("click", function() {

    if (state === 0) {
      display.value += parseInt(this.value, 10);
    } else if (state === 1) {
      reset();
      display.value += parseInt(this.value, 10);
      state = 0;
    }

  })
}

// Iterates through operator elements and sets event listeners
for (var i = 0; i < operator.length; i++) {
  operator[i].addEventListener("click", function() {
    const prevIndex = display.value.substring(display.value.length - 1);

    // if previous value is an operator, a new clicked operator will replace it
    if (prevIndex === "*" || prevIndex === "+" || prevIndex === "-" || prevIndex === "/" || prevIndex === ".") {
      display.value = display.value.slice(0, -1);
      display.value += this.value;
    } else if (display.value.length > 0) {
      display.value += this.value;
      state = 0;
    }
  })
}

// clears display value
clear.addEventListener("click", function() {
  reset();
})

// deletes previous value on display
backSpace.addEventListener("click", function() {
  display.value = display.value.slice(0, -1);
})

// Evaluates expression on display
equals.addEventListener("click", function() {
  display.value = eval(display.value);
  state = 1;
})