如何在javascript中获取特定键的值

Question

I have this Object

const fruits = {
    apple: 28,
    orange: 17,
    pear: 54,
};

I want to insert the values from the key "apple" into an empty array

with Object.values.fruits I get all the values, so I tried it with Object.values(fruits.apple) to specify the key

const leere_liste = [];

const values = Object.values(fruits);

leere_liste.push(values);

but this gives my an empty array, is there a method for that which I'm unaware of ?

Answer 1

Couple of things.

Its Object.values(fruits) , not Object.values.fruits .

Object.values only works on objects. So while it will work on fruits , it won't work on a specific property of fruits unless that property contains an object too.

Works:

const fruits = {apple: 28, orange: 17, pear: {a: 54, b: 22}};

console.log(Object.values(fruits.pear));
// [54, 22]

Also, since you're getting an array back from Object.values , if you push that onto another array you'll just have an array containing an array of those values.

If you want a single dimensional array, simply assign it like:

const leere_liste = Object.values(fruits);

Answer 2

Not sure what " I get all the values, so I tried it with Object.values(fruits.apple) to specify the key" means, as in your code you are simply getting the values of the entire array, not just apple, and also the property apple itself doesn't have "values", it has only one value.

Object.values is a function that takes an object as a parameter and returns an array of all of the values of the object only, usually in alphabetical order of the keys, but the actual final product has no connection to the original keys or the object, just given it itself it would be impossible to determine what values correspond to what keys

Hence it's a bit difficult to understand what you are trying to do, if you are trying to only insert the value of "apples" into an empty array, I don't know why you can't just do emptyArray.push(fruits.apple) , if you are trying to make a method for pushing the value of any given fruit to an array, you can simply use bracket notation on a function const fruity= (arr, obj, key) => arr.push(obj[key]) then to use it with your variables fruity(leere_liste, fruits, "apple")

If you want to convert the keys AND values into a new kind of array that you can work with, then what you need is Object.entries , it is a function that takes an object as a parameter and returns a two dimensional array, with the first element of each sub array representing the key of the respective object property, and the second element of each sub array representing the corresponding value to said key of the original object.

To use it just call var newArray=Object.entries(fruits) , in general this is helpful if you want to modify objects using expressions, such as Array.map, Array.forEach etc, although I'm not sure if you need it to simply add a property of an object to an array, to do that, see paragraphs above