使用forEach映射对象数组的Object.entries返回未定义，除非使用console.log

我最终想要提取这些值，以将它们分配给Victory BarChart的Y轴.感谢您的任何见解/指导.解决方案 .forEach 不返回值或数组.尝试改用 .map .另外，在这种情况下，您不需要Java语言的 Map (它不能有重复的键)，而且还要考虑到Victory BarChart似乎将 Array 作为数据(不是 Map ).这是我建议的更改: const mapTest = filterCounties.map(元素=>({'Penetration_2018':element ['Penetration_2018']})) I have an array of objects that have key value pairs, I want to find a specific key in each object and return the value.A sample of the Array:filterCounties=[ { "StateName": "Delaware", "CountyName": "Kent", "FIPS": 10001, "Eligibles_2017": 33292, "Eligibles_2018": 34938, "Penetration_2017": 0.107, "Penetration_2018": 0.123 }, { "StateName": "Delaware", "CountyName": "New Castle", "FIPS": 10003, "Eligibles_2017": 94030, "Eligibles_2018": 98080, "Penetration_2017": 0.128, "Penetration_2018": 0.164 }, { "StateName": "Delaware", "CountyName": "Sussex", "FIPS": 10005, "Eligibles_2017": 61964, "Eligibles_2018": 65990, "Penetration_2017": 0.082, "Penetration_2018": 0.097 }, { "StateName": "Delaware", "CountyName": "Pending County Designation", "FIPS": 10, "Eligibles_2017": 9, "Eligibles_2018": 0, "Penetration_2017": 0, "Penetration_2018": 0 }]The key I am looking for is Penetration_2018 - I can use the following code and output the values using console.logconst mapTest = new Map( Object.entries(filterCounties).forEach(([key, value]) => console.log((key, value["Penetration_2018"])) ) );This will output the values:console.log outputHowever if I assign to a variable and then log the variable const mapTest = new Map( Object.entries(filterCounties).forEach( ([key, value]) => (key, value["Penetration_2018"]) ) ); console.log(`This is mapTest ${mapTest}`);I get [object Map] with no values - I thought that when using an arrow function, return was implicit?Image of output - with or without String concatenation enter image description hereI ultimately want to extract these values to assign them to the Y axis of a Victory BarChart. Thanks for any insight / guidance. 解决方案 .forEach does not return a value or an array. Try using .map instead. Also, you don't need a Javascript Map in this case (it can't have repeated keys), considering furthermore that Victory BarChart seems to take an Array as data (not a Map).This is my suggested change:const mapTest = filterCounties.map( element => ({'Penetration_2018': element['Penetration_2018']})) 这篇关于使用forEach映射对象数组的Object.entries返回未定义，除非使用console.log的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 1403页，肝出来的..