程序不会使用数学方法返回最大值或最小值答案

【问题标题】：Program won't return highest or smallest values using math methods程序不会使用数学方法返回最大值或最小值
【发布时间】：2021-03-06 23:09:00
【问题描述】：

帮助我试图让我的代码发出警报最重要的数字输入和最低的为什么我的不这样做？

let price;
let items = 0; 
let sum=0;
let big = 0 ;
let small = 0;

price = Number(prompt("Please enter the price of the Item you choose to buy or enter -1 to stop: "));

while (price != -1){

    sum=sum+price;
    items++;
    avg = sum/items;
    Big = Math.max(Number(price));
    small = Math.min(Number(price));
    price = Number(prompt("Please enter the price of the Item you choose to buy or enter -1 to stop: "));
    
   
}

alert("You have purchased "+items+" items!");
alert("the sum of items you purchased is: $"+sum);
alert("the Averege of the items is: " + avg);
alert("The highest item price purchased was: "+ Big);
alert("The lowest item price was: "+ small);

【问题讨论】：

你必须给Math.max()多个参数。它返回所有参数中最高的。
如果你只给它一个参数，它只会返回那个，因为没有其他东西可以比较。
你为什么写Number(price)？您在分配变量时将其转换为数字，您不必再次转换它。
如何获得最高的输入回报
比较当前输入和Big。如果更高，请替换Big。

标签： javascript math methods while-loop

【解决方案1】：

使用函数 isNumeric 检查valid numbers。使用名为itemsPurchased的数组存储所有有效购买not including empty string, negative numbers。

使用template strings, destructuring assignment, Array.prototype.reduce() , Math.max(), spread operator , Math.min() and Array.prototype.length 得到想要的结果。

function isValidNumber(str) {
  if (typeof str != "string") return false;
  return (
    !isNaN(str) && 
    !isNaN(parseFloat(str))
  );
}

function purchaseCalculation() {
  let price,
    expensive,
    cheap,
    itemsNumber,
    average,
    total,
    itemsPurchased = [];

  price = prompt(
    "Please enter the price of the Item you choose to buy or enter -1 to stop: "
  );
  while (price !== "-1") {
    if (isValidNumber(price) && Number(price) >= 0) {
      itemsPurchased.push(Number(price));
    }
    price = prompt(
      "Please enter the price of the Item you choose to buy or enter -1 to stop: "
    );
  }

  expensive = itemsPurchased.length === 0 ? 0 : Math.max(...itemsPurchased);
  cheap = itemsPurchased.length === 0 ? 0 : Math.min(...itemsPurchased);
  total = itemsPurchased.reduce((total, item) => total + item, 0);
  itemsNumber = itemsPurchased.length;
  average = total === 0 ? 0 : total / itemsNumber;

  return [cheap, expensive, total, itemsNumber, average];
}


const [cheap, expensive, total, itemsNumber, average] = purchaseCalculation();
alert(
  `You have purchased ${itemsNumber} ${itemsNumber > 1 ? "items" : "item"}!`
);
alert(
  `The sum of ${
    itemsNumber > 1 ? "items" : "item"
  } you purchased was: $${total}`
);
alert(
  `The average of the ${itemsNumber > 1 ? "items" : "item"} was: ${average}`
);
alert(`The highest item price purchased was: ${expensive}`);
alert(`The lowest item price was: ${cheap}`);

【讨论】：