如何使用JavaScript获取嵌套数组中特定值的最大值和最小值？

Question

I want to take the maximum and the minimum of specific values in a nested array.

An example would be a nested array being in the format [latitude, longitude].

The nested array I want to input is [[40, 50], [50, 60], [60, 70]].

Max longitude should output 70 and min longitude should output 50.

Max latitude should output 60 and min latitude should output 40.

Average longitude should output 60 and average latitude should output 50.

Now my question is how do I take the max and min values of longitude and latitude values in the nested array and find the average separately using JavaScript?

Answer 1

What about something like this:

var numbers = [[1, 5], [2, 3], [4,10]];
// max for o[0];
Math.max.apply(Math, numbers.map(function(o) { return o[0]; }));
4
// max for o[1]
Math.max.apply(Math, numbers.map(function(o) { return o[1]; }));
10
// min for o[0]
Math.min.apply(Math, numbers.map(function(o) { return o[0]; }));
1
// min for o[1]
Math.min.apply(Math, numbers.map(function(o) { return o[1]; }));
3

Hope it helps

Answer 2

 const latlon = [[40, 50], [50, 60], [60, 70]] const lat = latlon.map(a => a[0]) const lon = latlon.map(a => a[1]) const maxLat = Math.max(...lat) const minLat = Math.min(...lat) const avgLat = (lat.reduce((acc,cur) => acc + cur, 0))/lat.length console.log(maxLat, minLat, avgLat) const maxLon = Math.max(...lon) const minLon = Math.min(...lon) const avgLon = (lon.reduce((acc,cur) => acc + cur, 0))/lon.length console.log(maxLon, minLon, avgLon) 

Answer 3

Using the Array#reduce method, you could achieve this in a "functional" way.

Each method begins the reduction with an initial value taken from the input array, and then iterates through the array searching for and updating the current minimum or maximum in the array as it goes.

Following with this approach, the "average" methods are implemented by composing both the "minimum" and "maximum" methods, and averaging the numeric result that they return:

 var array = [[40, 50], [50, 60], [60, 70]] const findMinLatitude = (arr) => { return arr.reduce((min, item) => { return Math.min(min, item[0]) }, arr[0][0]) } const findMaxLatitude = (arr) => { return arr.reduce((max, item) => { return Math.max(max, item[0]) }, arr[0][0]) } const findAvgLatitide = (arry) => { return (findMinLatitude(arry) + findMaxLatitude(arry)) * 0.5 } const findMinLongitude = (arr) => { return arr.reduce((min, item) => { return Math.min(min, item[1]) }, arr[0][1]) } const findMaxLongitude = (arr) => { return arr.reduce((max, item) => { return Math.max(max, item[1]) }, arr[0][1]) } const findAvgLongitude = (arry) => { return (findMinLongitude(arry) + findMaxLongitude(arry)) * 0.5 } console.log('Min latitude', findMinLatitude(array)) console.log('Max latitude', findMaxLatitude(array)) console.log('Average latitude', findAvgLatitide(array)) console.log('Min longitude', findMinLongitude(array)) console.log('Max longitude', findMaxLongitude(array)) console.log('Average longitude', findAvgLongitude(array))