我想找到最大的变化答案

【问题标题】：I want to find Biggest Change我想找到最大的变化
【发布时间】：2021-09-19 11:40:04
【问题描述】：

我的脚本不能只打印数据中的最后一个标记，我的脚本应该打印 zil，因为它是我数据中最大的变化

var olddata = 
[
    {"token": "NORD", "oldprice": 1},
    {"token": "DYP", "oldprice": 2.43},
    {"token": "ZIL", "oldprice": 0.20},
    {"token": "VET", "oldprice": 6.33}
]

var newdata = 
[
    {"token": "NORD", "newprice": 1.20},
    {"token": "DYP", "newprice": 2.80},
    {"token": "ZIL", "newprice": 0.40},
    {"token": "VET", "newprice": 6.90}
]
function findBiggestChange(oldData, newData) {
  var previousDifference = null;
  var changeIndex;
  oldData.forEach((obj, i) => {
    var data = newData.find(d => d.token === obj.token);
        var currentDifference = previousDifference ? Math.abs.forEach(data.newprice - obj.oldprice) : data.newprice;
        changeIndex = currentDifference > previousDifference ? i : 0;
  });
}

findBiggestChange(olddata,newdata);

【问题讨论】：

标签： javascript node.js arrays math foreach

【解决方案1】：

我们可以使用Array.map 创建一个变化列表，包括绝对（变化）和百分比（百分比变化）。

使用Array.sort，然后我们将按百分比变化的降序排序以获得最大的百分比变化：

const olddata = [ {"token": "NORD", "oldprice": 1}, {"token": "DYP", "oldprice": 2.43}, {"token": "ZIL", "oldprice": 0.20}, {"token": "VET", "oldprice": 6.33} ]
const newdata = [ {"token": "NORD", "newprice": 1.20}, {"token": "DYP", "newprice": 2.80}, {"token": "ZIL", "newprice": 0.40}, {"token": "VET", "newprice": 6.90} ] 

// Get the percentage change and absolute change of each value...
const changes = olddata.map(({token, oldprice}, idx) => {
    const change = (newdata[idx].newprice - oldprice);
    const percentageChange = 100 * change / oldprice;
    return { token, percentageChange, change };
});

// Sort by percentage change, in descending order
const sortedByPercentChange = changes.sort((a, b) => b.percentageChange - a.percentageChange);

console.log("All changes (sorted on % change):", sortedByPercentChange)

// The largest change will be the first element...
console.log("Largest % change:", sortedByPercentChange[0])

【讨论】：

【解决方案2】：

以下代码为您提供 zil 对象作为结果，因为它具有最大的差异。

var olddata = 
[
    {"token": "NORD", "oldprice": 1},
    {"token": "DYP", "oldprice": 2.43},
    {"token": "ZIL", "oldprice": 0.20},
    {"token": "VET", "oldprice": 6.33}
]

var newdata = 
[
    {"token": "NORD", "newprice": 1.20},
    {"token": "DYP", "newprice": 2.80},
    {"token": "ZIL", "newprice": 0.40},
    {"token": "VET", "newprice": 6.90}
]
function findBiggestChange(oldData, newData) {
  var previousDifference = null;
  var changeIndex;
  oldData.forEach((obj, i) => {
    var data = newData.find(d => d.token === obj.token);
    var currentDifference = (data.newprice/obj.oldprice) - (1);
    if (!previousDifference) {
        previousDifference = currentDifference;
    }  
    if (currentDifference > previousDifference) {
        changeIndex = i;
        previousDifference = currentDifference;
    }
  });
  return oldData[changeIndex];
}

console.log(findBiggestChange(olddata,newdata));

【讨论】：

【解决方案3】：

如果您的意思是数量上的“最大变化”，那么您的程序是正确的。因为：

ZIL：0.40 - 0.20 = 0.20

VET：6.90 - 6.33 = 0.57（VET 增幅在数量上更高）

如果您的“最大变化”是按百分比计算的，那么您需要更改检查百分比变化的方式，而不是数量方面的变化。在这种情况下，最大的变化是……：

ZIL：0.40/0.20 = 2 => 2 - 1 = 1 = 100%（ZIL百分比增加更高）

兽医：6.90/6.33 = 1.09 => 1.09 - 1 = 0.09 = 9% 兽医：6.90/6.33 = 1.09 => 1.09 - 1 = 0.09 = 9%

如果您的“最大变化”是百分比，您要查找的代码是：

var olddata = 
[
    {"token": "NORD", "oldprice": 1},
    {"token": "DYP", "oldprice": 2.43},
    {"token": "ZIL", "oldprice": 0.20},
    {"token": "VET", "oldprice": 6.33}
];

var newdata = 
[
    {"token": "NORD", "newprice": 1.20},
    {"token": "DYP", "newprice": 2.80},
    {"token": "ZIL", "newprice": 0.40},
    {"token": "VET", "newprice": 6.90}
];

function findBiggestChange(oldData, newData) {
  var biggestDifference = -Infinity;
  var biggestChangeObject = null;
  oldData.forEach(obj => {
    var data = newData.find(d => d.token === obj.token);
    var currentDifference = (data.newprice/obj.oldprice) - 1;
    
    if (currentDifference > biggestDifference) {
        biggestDifference = currentDifference;
        biggestChangeObject = obj;
    }
  });
  return biggestChangeObject;
}

console.log(findBiggestChange(olddata,newdata));

【讨论】：