Getting JavaScript object key list vol. 2

Question

Here is original question: Getting JavaScript object key list

But if the situation is little bit more complex like:

var obj = [
   { key1: 'value1' },
   { key2: 'value2' },
   { key3: 'value3' },
   { key4: 'value4' }
]

Then how you get keys like that?

[key1,key2,key3,key4]

Answer 1

You can use mix of Object.keys and Array#flatMap.

let obj = [
   { key1: 'value1' },
   { key2: 'value2' },
   { key3: 'value3' },
   { key4: 'value4' },
];

let keys = obj.flatMap(Object.keys);

console.log(keys);