如何使用带有Object.keys函数的$ .map从给定Object.keys的数组中获取第一个值？

Question

I have this json array:

//val
0: {name: "jeg", class: "klase-jeg", id: "id-jeg"} 1: {age: 11, id: "jeg-id-11"} 2: {mail: "jeg mail", class: "jeg-klas-mail"}

and i want to get the first key of each json:

(name,age,mail)

This is my function:

$.map(val, Object.keys) //Result: ["name", "class", "id", "age", "id", "mail", "class"]

But the result is all the keys.

to get the first key from a json i used this:

obj = val[0]; Object.keys(obj)[0]); //Result: name

and i tried to use it with map but it didnt work :(

$.map(val, Object.keys[0]) //failed

i can use each or for, but i would like to know if can i use map with object.key to get the first key of each json.

Thanks!

Answer 1

I think you could do this :

assuming :

a = [{name: "jeg", class: "klase-jeg", id: "id-jeg"},{age: 11, id: "jeg-id-11"},{mail: "jeg mail", class: "jeg-klas-mail"}]

then do :

    a.map((el)=>{
    return Object.keys(el)[0];
    });

Hope it helps !

Answer 2

You can use map and Object.keys like this:

 const val = [ {name: "jeg", class: "klase-jeg", id: "id-jeg"}, {age: 11, id: "jeg-id-11"}, {mail: "jeg mail", class: "jeg-klas-mail"}] const firstKeys = val.map(a => Object.keys(a)[0]); console.log(firstKeys) /* In jquery: $.map(val, a => Object.keys(a)[0]) */ 

$.map(val, Object.keys[0]) will throw an error because Object.keys is a function , not an array.

Update: Please note that properties' order in objects is not guaranteed in javaScript