如何将父 object 的 id 推送到子对象？

Question

I have an array of object which has an inner array of object, I want to push the id of parent object to each child object.

   a = [
        {id: 'abc', stage: [{name: 'car' , value: '123'},{name: 'bus' , value: '345'},{name: 'truck' , value: '567'}],
        {id: 'def', stage: [{name: 'bike' , value: '890'},{name: 'cycle' , value: '123'},{name: 'car' , value: '456'}]}
    ]

expected output = [
    {name: 'car' , value: '123', id: 'abc'},{name: 'bus' , value: '345', 'abc'},{name: 'truck' , value: '567', 'abc'}, {name: 'bike' , value: '890', id: 'def'},{name: 'cycle' , value: '123',id: 'def',id: 'def'},{name: 'car' , value: '456', id: 'def'}
]

Im able to get the only the stage but not able to push id to each object. pls help

const getAllStages = [].concat(...map(a, el => el.stage));
console.log(getAllStages )

Answer 1

Use .map() again to add el.id to each element of el.stage .

You can use .flatMap() in the outer mapping to concatenate all the results into a single array.

 const a = [ {id: 'abc', stage: [{name: 'car', value: '123'},{name: 'bus', value: '345'},{name: 'truck', value: '567'}]}, {id: 'def', stage: [{name: 'bike', value: '890'},{name: 'cycle', value: '123'},{name: 'car', value: '456'}]} ] result = a.flatMap(({ id, stage }) => stage.map(s => ({ id: id, ...s }))); console.log(result);

Answer 2

You can write like this without using libraries

let a = [
    {
        id: 'abc', stage:
            [
                { name: 'car', value: '123' },
                { name: 'bus', value: '345' },
                { name: 'truck', value: '567' }
            ]
    },
    {
        id: 'def', stage:
            [
                { name: 'bike', value: '890' },
                { name: 'cycle', value: '123' },
                { name: 'car', value: '456' }
            ]
    }
]    
let output = [];
    for (const element of a) {
        for (const stageElement of element.stage) {
            let newElement = {
                name: stageElement.name,
                value: stageElement.value,
                id: element.id
            };
            output.push(newElement);
        }
    }

Answer 3

If you're trying to merge in id :

let remapped = a.map(e => ({ id: a.id, ...e }));

Where that converts each entry into an object inheriting the a.id value and adding on whatever else is in the object.

Answer 4

Here is a example and result:)

a.forEach(function(row) {
    row.stage.map(function (child) {child.id = row.id})
})

result:

[{"id":"abc","stage":[{"name":"car","value":"123","id":"abc"},{"name":"bus","value":"345","id":"abc"},{"name":"truck","value":"567","id":"abc"}]},{"id":"def","stage":[{"name":"bike","value":"890","id":"def"},{"name":"cycle","value":"123","id":"def"},{"name":"car","value":"456","id":"def"}]}]

Answer 5

const a = [
    {id: 'abc', stage: [{name: 'car' , value: '123'},{name: 'bus' , value: '345'},{name: 'truck' , value: '567'}]},
    {id: 'def', stage: [{name: 'bike' , value: '890'},{name: 'cycle' , value: '123'},{name: 'car' , value: '456'}]}
]

a.forEach(item => {
    const itemId = item.id;
    const stages = item.stage;

    stages.forEach(stage => {
        stage['id'] = itemId;
    })
});

console.log(a);