Вы можете использовать reduce
вместе с map
:
var res = [{
"id": 1,
"type_name": "Weight",
"type_abbr": "wt",
"uoms": [{
"id": 1,
"unit_abbr": "sh tn",
"unit_name": "Short Tons",
"created_at": "2017-06-07 00:35:06",
"updated_at": "2018-05-24 23:34:25",
"uom_type_id": 1
},
{
"id": 3,
"unit_abbr": "g",
"unit_name": "Grams",
"created_at": "2017-06-07 00:35:06",
"updated_at": "2018-05-24 23:34:25",
"uom_type_id": 1
}
]
},
{
"id": 2,
"type_name": "Weight",
"type_abbr": "wt",
"uoms": [{
"id": 11,
"unit_abbr": "sh tn",
"unit_name": "Short Tons 2",
"created_at": "2017-06-07 00:35:06",
"updated_at": "2018-05-24 23:34:25",
"uom_type_id": 11
},
{
"id": 31,
"unit_abbr": "g",
"unit_name": "Grams 2",
"created_at": "2017-06-07 00:35:06",
"updated_at": "2018-05-24 23:34:25",
"uom_type_id": 31
}
]
}
]
console.log(res.reduce((a, r) => [...a , ...r.uoms.map(u => u.unit_name)], []))