Grouping JSON by values

Assume , the JSON output is

outJSON= 
 [ {
      team: "TeamA",
      name: "Ahmed",
      field3:"val3"
  }, 
{
      team: "TeamB",
      name: "Ahmed",
      field3:"val43"
  }, 
{
      team: "TeamA",
      name: "Ahmed",
      field3:"val55"
  }, 


]

Then see the groupBy function in the DEMO below:

DEMO :

outJSON= [ {team: "TeamA",name: "Ahmed",field3:"val3"}, {team: "TeamB",name: "Ahmed",field3:"val43"}, {team: "TeamA",name: "Ahmed",field3:"val55"} ]

var groupBy = function(xs, key) {
  return xs.reduce(function(rv, x) {
    (rv[x[key]] = rv[x[key]] || []).push(x);
    return rv;
  }, {});
};
var groubedByTeam=groupBy(outJSON, 'team')
console.log(groubedByTeam);

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Then , if you want to loop through categories (teams), get all categories in array :

Object.keys(groubedByTeam) // return ["TeamA","TeamB"]

then :

  Object.keys(groubedByTeam).forEach(function(category){

       console.log(`Team ${category} has ${groubedByTeam[category].length} members : `);
        groubedByTeam[category].forEach(function(memb,i){
              console.log(`---->${i+1}. ${memb.name}.`)
       })
  }); 

[출처] https://stackoverflow.com/questions/38575721/grouping-json-by-values