转换 JavaScript 数组，创建表格视图

Question

我已经搜索过类似的问题并试图自己解决问题，但我的编程能力很弱。

我有一个类似的数组：

[{"city": "Amsterdam", "year": "2013", "amount": "450"},
 {"city": "Rotterdam", "year": "2013", "amount": "620"},
 {"city": "Geneva",    "year": "2014", "amount": "530"},
 {"city": "Rotterdam", "year": "2015", "amount": "350"}]

我想使用“城市”和“年份”对其进行转换以获得“金额”。例如。鹿特丹：[620,N/A,350]。 “N/A”，因为缺少 2014 年的值。 我正在检查地图功能等，但我的技能很弱。 最后，我想创建一个包含年份（水平）和城市（垂直）的表格视图。 请指教。谢谢

Answer 1

我认为这不是编程技能，而是算法技能。这是一个做你想做的代码：

var amounts = [{"city": "Amsterdam", "year": "2013", "amount": "450"},{"city": "Rotterdam", "year": "2013", "amount": "620"},{"city": "Geneva", "year": "2014", "amount": "530"},{"city": "Rotterdam", "year": "2015", "amount": "350"}],
    formattedAmounts = {}
;
             
for (var i = 0; i < amounts.length; i++) {
    var amount = amounts[i];
  
    if (undefined === formattedAmounts[amount.city]) {
        formattedAmounts[amount.city] = {};
    }

    formattedAmounts[amount.city][amount.year] = amount.amount;
}

console.log(JSON.stringify(formattedAmounts));
alert(JSON.stringify(formattedAmounts));

function getCityAmount(city) {
    var years = [2013, 2014, 2015],
        cityAmounts = []
    ;

    for (var i = 0; i < years.length; i++) {
        cityAmounts.push(
            formattedAmounts[city] && formattedAmounts[city][years[i]]
                ?  formattedAmounts[city][years[i]]
                : 'N/A'
        );
    }

    return cityAmounts;
}

console.log(JSON.stringify(getCityAmount('Amsterdam')));
alert(JSON.stringify(getCityAmount('Amsterdam')));

function getCitiesAmounts() {
    var citiesAmounts = [];

    for (var i = 0; i < amounts.length; i++) {
        citiesAmounts.push(getCityAmount(amounts[i].city));
    }

    return citiesAmounts;
}

console.log(JSON.stringify(getCitiesAmounts()));
alert(JSON.stringify(getCitiesAmounts()));