javascript - 如何计算 JSON 中特定元素的数量

Question

我有一个 JSON 对象，如下所示:

var allDataJson = [{"Researchers":"Laura, Mikael","Year":"2015"}, 
{"Researchers":"Mikko","Year":"2013",}, 
{"Researchers":"Harri","Year":"2015"}, .......] //long list 

我需要创建一个 JSON 对象，如下所示:

 var myjson = [{"Year": 2015, "Total":60}, 
                  {"Year": 2014, "Total":68},
                  {"Year": 2013, "Total":72}]

例如，有 60 个 2015 年的 allDataJson 项。

到目前为止，我只能获取年份值。关于如何计算Total有什么想法吗？

这是我的代码:

function countPublicationsPerYear(allDataJson){
    var lookup = {};
    var items = allDataJson;
    var result = [];

    for (var item, i = 0; item = items[i++];) {
        var year = item.Year;
        count ++;
        if (!(year in lookup)) {
            var count = Object.keys(item).length;
            lookup[year] = 1;
            result.push({ "Year":year
            });
        }
    }
    return result; //returns Year: 2013, 2014, 2015
}

Answer 1

所以您正在尝试增加研究人员总数？

回答

function countPublicationsPerYear(allDataJson){
    var lookup = {};
    var items = allDataJson;
    var result = [];

    for (var item, i = 0; item = items[i++];) {
        var year = item.Year;
        count ++;
        if (!(year in lookup)) {
            lookup[year] = 1;
        } else {
            lookup[year]++;
        }
    }

    for (var property in lookup) {
        if (lookup.hasOwnProperty(property)) {
            result.push({"Year": property, "Total": lookup[property]});
        }
    }

    return result; //returns Year: 2013, 2014, 2015
}

var allDataJson = [{"Researchers":"Laura, Mikael","Year":"2015"}, 
{"Researchers":"Mikko","Year":"2013",}, 
{"Researchers":"Harri","Year":"2015"}];

function countPublicationsPerYear(allDataJson){
        var lookup = {};
        var items = allDataJson;
        var result = [];
    
        for (var item, i = 0; item = items[i++];) {
            var year = item.Year;
            if (!(year in lookup)) {
                lookup[year] = 1;
            } else {
                lookup[year]++;
            }
        }
    
        for (var property in lookup) {
            if (lookup.hasOwnProperty(property)) {
                result.push({"Year": property, "Total": lookup[property]});
            }
        }
    
        alert(JSON.stringify(result));
  
        return result; //returns Year: 2013, 2014, 2015
    }

countPublicationsPerYear(allDataJson);