How to chain map and filter methods for a complex array of objects in Javascript?

Question

I have an array as following:

var arr = [
    {                                                   
        subArray1:[
            {
                subArray2:[
                    {
                        value: 1
                    },
                    {
                        value: 0
                    }
                ]
            },
            {
                subArray2:[
                    {
                        value: 1
                    },
                    {
                        value: 0
                    }
                ]
            }
        ]
    }
];

I want to filter out all objects inside the subArray2 that contains value 1 and return the whole array. The expected output is as follows:

newArr= [
    {                                                   
        subArray1:[
            {
                subArray2:[
                    {
                        value: 1
                    }
                ]
            },
            {
                subArray2:[
                    {
                        value: 1
                    }
                ]
            }
        ]
    }
]

I am unable to chain the map and filter methods in such a way that I get the above desired output. Please help me to achieve that.

Will it always be only two nested arrays, or does it have to account for the fact that you might have more layers? — CVerica
– CVerica, Commented Jun 2, 2021 at 20:53
There's always a solution... it would just be more complicated. — CVerica
– CVerica, Commented Jun 2, 2021 at 21:56

dave · Accepted Answer · 2021-06-02 20:55:59Z

You'll need to map each arr item, and each arr.subArray1 item, and then filter subArray2:

var arr = [
    {                                                   
        subArray1:[
            {
                subArray2:[
                    {
                        value: 1
                    },
                    {
                        value: 0
                    }
                ]
            },
            {
                subArray2:[
                    {
                        value: 1
                    },
                    {
                        value: 0
                    }
                ]
            }
        ]
    }
];

console.log(
    arr.map(({...el}) => {
        el.subArray1 = el.subArray1.map(({...el1}) => {
            el1.subArray2 = el1.subArray2.filter(({value}) => value !== 0);
            return el1;
        });
        return el;
    })
)

Ele · Accepted Answer · 2021-06-02 21:08:51Z

Assuming there are only those nested arrays, you can use the function reduce along with the function filter.

const arr = [    {                                                           subArray1:[            {                subArray2:[                    {                        value: 1                    },                    {                        value: 0                    }                ]            },            {                subArray2:[                    {                        value: 1                    },                    {                        value: 0                    }                ]            }        ]    }],
      result = arr.reduce((a, {subArray1}) => {
      a.push({
        subArray1: subArray1.reduce((a, {subArray2}) => {
            a.push({subArray2: subArray2.filter(({value}) => value === 1)});
            return a;
          }, [])
        });
        
        return a;
      }, []);
      
console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

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