javascript array group by
function groupByKey(array, key) {
return array
.reduce((hash, obj) => {
if(obj[key] === undefined) return hash;
return Object.assign(hash, { [obj[key]]:( hash[obj[key]] || [] ).concat(obj)})
}, {})
}
var cars = [{'make':'audi','model':'r8','year':'2012'},{'make':'audi','model':'rs5','year':'2013'},{'make':'ford','model':'mustang','year':'2012'},{'make':'ford','model':'fusion','year':'2015'},{'make':'kia','model':'optima','year':'2012'}];
var result = groupByKey(cars, 'make');
JSON.stringify(result,"","\t");
{
"audi": [
{
"make": "audi",
"model": "r8",
"year": "2012"
},
{
"make": "audi",
"model": "rs5",
"year": "2013"
}
],
"ford": [
{
"make": "ford",
"model": "mustang",
"year": "2012"
},
{
"make": "ford",
"model": "fusion",
"year": "2015"
}
],
"kia": [
{
"make": "kia",
"model": "optima",
"year": "2012"
}
]
}