使用另一个对象的键和值创建一个新对象

Question

I'm saving an object in state that looks like:

ingredients: {
        salad: {
            amount: 3,
            basePrice: 1
        },
        cheese: {
            amount: 2,
            basePrice: 1.2
        }
}

I want to use this in my component's state as follows

    ingredients: {
    salad: 3,
    cheese: 2
}

I used Object.keys and map at first but it returns an Array of key value pairs instead of objects.

Although this works:

  const newIngredientsObject = {}; for (const i in ingredientsObject) newIngredientsObject[i] = ingredientsObject[i].amount; return newIngredientsObject; 

I want to find a solution without a helper method, as such:

 const mapStateToProps = state => { return { ingredients: Object.keys(state.burger.ingredients).map(i => ( { [i]: state.burger.ingredients[i].amount } )), totalPrice: state.burger.totalPrice } }; 

Answer 1

You could map the entries of the object by using the amount property of the values and take Object.assign for getting a new object.

 var ingredients = { salad: { amount: 3, basePrice: 1 }, cheese: { amount: 2, basePrice: 1.2 } }, result = Object.assign( ...Object.entries(ingredients).map(([key, value]) => ({ [key]: value.amount })) ); console.log(result); 

Answer 2

when you want to create one object to inside to another go this web

object 1  = {
content 1 = {
    stuff = {
    },
    more Stuff = {
    }
}

} object 2 = { key 1:"", key 2:""

} object 1.content 1 = object 2;

Answer 3

You asked a solution with Object.keys, here is one:

var x = {ingredients: {
        salad: {
            amount: 3,
            basePrice: 1
        },
        cheese: {
            amount: 2,
            basePrice: 1.2
        }
}}

Object.keys(x.ingredients).map((d,i)=>[d,x.ingredients[d].amount]).reduce((ac,d,i)=>(ac[d[0]]=d[1],ac),{})

//{salad: 3, cheese: 2}

Answer 4

The shortest I could come up with it using Object.keys and reduce

 const ingredients = { salad: { amount: 3, basePrice: 1 }, cheese: { amount: 2, basePrice: 1.2 } }; let newObject = Object.keys(ingredients).reduce((acc, val) => { acc[val] = ingredients[val].amount; return acc; }, {}); console.log(newObject); 

Answer 5

ANSWER : Thanks for the solutions provided by @ibowankenobi and @Nina Scholz

• Reduce function:

 Object.keys(ingredients) .map( (d, i) => [d, ingredients[d].amount]) .reduce( (ac, d, i) => (ac[d[0]] = d[1], ac), {} ); 

• Entries function:

 Object.assign(...Object.entries(ingredients) .map( ([key, value]) => ({ [key]: value.amount }) ) ); 

reduce: 0.0849609375ms
entries: 0.1650390625ms
forLoop: 0.07421875ms
reduce: 0.024169921875ms
entries: 0.048095703125ms
forLoop: 0.010009765625ms
reduce: 0.010009765625ms
entries: 0.016845703125ms
forLoop: 0.0078125ms

After some testing, it seems like using a for loop is the most efficient and after that the reduce function.