如何从json对象中的max属性获取对象属性

Question

I have the following array of objects. I need to obtain the properties of the item which has the highest MoveCount . I have a function which returns me only the MoveCount . But I want to get the value of Latitude and Longitude as well.

The function I used is as follows:

var res = Math.max.apply(Math,movers.map(function(o){
return o.MoveCount, o.Latitude, o.Longitude;}))

alert('Max y = ' + res);

Objects:

var movers = [{"MoveCount":3,"DepartureCountryCode":"MG","Latitude":-18.766947,"Longitude":46.869107},
{"MoveCount":2,"DepartureCountryCode":"MU","Latitude":-20.348404,"Longitude":57.552152},
{"MoveCount":4,"DepartureCountryCode":"ZA","Latitude":-30.559482,"Longitude":22.937506}];

Answer 1

You can use a custom sort function based on MoveCount. This would retain the entire object as it is.

 var movers = [ { "MoveCount":3, "DepartureCountryCode":"MG", "Latitude":-18.766947, "Longitude":46.869107 }, { "MoveCount":2, "DepartureCountryCode":"MU", "Latitude":-20.348404, "Longitude":57.552152 }, { "MoveCount":4, "DepartureCountryCode":"ZA", "Latitude":-30.559482, "Longitude":22.937506 } ]; movers.sort(function(a,b){ return b.MoveCount - a.MoveCount; }); var highestMoveCount = movers[0]; // get the item with the highest MoveCount console.log(highestMoveCount); 

The above code returns an array sorted descending by MoveCount.

Answer 2

Sort the array, use map function to change the outcoming objects and get the first item from the sorted array.

 var movers = [ { "MoveCount": 3, "DepartureCountryCode": "MG", "Latitude": -18.766947, "Longitude": 46.869107 }, { "MoveCount": 2, "DepartureCountryCode": "MU", "Latitude": -20.348404, "Longitude": 57.552152 }, { "MoveCount": 4, "DepartureCountryCode": "ZA", "Latitude": -30.559482, "Longitude": 22.937506 }]; const highest = movers.sort((a,b) => b.MoveCount - a.MoveCount) .map(({MoveCount, Latitude, Longitude}) => ({MoveCount, Latitude, Longitude}))[0]; console.log(highest); 

Answer 3

您可以通过始终选择较大的动子来减少动子：

  const biggest = movers.reduce((max, mover) => max.MoveCount > mover.MoveCount ? max : mover);

Answer 4

You can sort as others say , but that would take O(nlogn) complexity. Or you can just compare the highest value in O(n) complexity.

 const movers = [{"MoveCount":3,"DepartureCountryCode":"MG","Latitude":-18.766947,"Longitude":46.869107}, {"MoveCount":2,"DepartureCountryCode":"MU","Latitude":-20.348404,"Longitude":57.552152}, {"MoveCount":4,"DepartureCountryCode":"ZA","Latitude":-30.559482,"Longitude":22.937506}] let highest = movers[0] for (let index=1; index<movers.length; index += 1) { let movObj = movers[index]; if (movObj.MoveCount > highest.MoveCount) { highest = movObj; } } console.log(highest) // if you only want certain fields const certainFieldsRes = ({MoveCount, Latitude, Longitude}) => ({ MoveCount, Latitude, Longitude }) console.log(certainFieldsRes(highest)) 

Answer 5

I'd probably use Array.prototype.reduce to traverse the array to find the item with the highest MoveCount .

 let movers = [ { "MoveCount":3, "DepartureCountryCode":"MG", "Latitude":-18.766947, "Longitude":46.869107 }, { "MoveCount":2, "DepartureCountryCode":"MU", "Latitude":-20.348404, "Longitude":57.552152 }, { "MoveCount":4, "DepartureCountryCode":"ZA", "Latitude":-30.559482, "Longitude":22.937506 } ]; let getHighestMoveCount = function (arr) { let o = arr.reduce(function (accumulator, currentValue, currentIndex) { // if this is the first item, we have nothing to compare against, // just return this item if (currentIndex === 0) { return currentValue; } else { // if this item has a higher MoveCount than the current highest, // return it if (currentValue.MoveCount > accumulator.MoveCount) { return currentValue; } else { // otherwise return the current highest return accumulator; } } }); // return the object that has the highest MoveCount return o; // This returns the entire object, if you wanted a new object with // only the MoveCount Latitude and Longitude, you would do // this instead: // return {MoveCount: o.MoveCount, Latitude: o.Latitude, Longitude: o.Longitude}; }; console.log(getHighestMoveCount(movers));