How to get an objects out from very complex deeply nested array of objects and arrays?-CodePudding

My data structure is very complex, can't figure out how to map through the data in a way so I can get what I want. There's a very big array with a lot of objects in it and each object has again arrays and objects nested in each other. The data looks like this:

const arr1 = [
  {
    id: 1,
    subject: 'Subject',
    chapters: [
      {
        name: 'chapter1',
        sections: [
          {
            name: 'section1',
            questions: [
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
            ],
          },
          {
            name: 'section2',
            questions: [
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
            ],
          },
        ],
      },
      {
        name: 'chapter2',
        sections: [
          {
            name: 'section1',
            questions: [
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
            ],
          },
          {
            name: 'section2',
            questions: [
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
            ],
          },
        ],
      },
    ],
  },
  {
    id: 2,
    subject: 'Subject',
    chapters: [
      {
        name: 'chapter1',
        sections: [
          {
            name: 'section1',
            questions: [
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
            ],
          },
          {
            name: 'section2',
            questions: [
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
            ],
          },
        ],
      },
      {
        name: 'chapter2',
        sections: [
          {
            name: 'section1',
            questions: [
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
            ],
          },
          {
            name: 'section2',
            questions: [
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
              {
                title: 'Title',
                subtitle: 'SubTitle',
              },
            ],
          },
        ],
      },
    ],
  },
];

How can I get an array from arr1 with only the objects located in 'questions' array, so it will look like this:

const arr2 = [
  {
    title: 'Title',
    subtitle: 'SubTitle',
  },
  {
    title: 'Title',
    subtitle: 'SubTitle',
  },
  {
    title: 'Title',
    subtitle: 'SubTitle',
  },
  {
    title: 'Title',
    subtitle: 'SubTitle',
  },
  {
    title: 'Title',
    subtitle: 'SubTitle',
  },
  {
    title: 'Title',
    subtitle: 'SubTitle',
  },
  {
    title: 'Title',
    subtitle: 'SubTitle',
  },
  {
    title: 'Title',
    subtitle: 'SubTitle',
  },
]

CodePudding user response：

Use flatMap

const arr1 = [{id: 1,subject: 'Subject',chapters: [{name: 'chapter1',sections: [{name: 'section1',questions: [{title: 'Title',subtitle: 'SubTitle',},{title: 'Title',subtitle: 'SubTitle',},],},{name: 'section2',questions: [{title: 'Title',subtitle: 'SubTitle',},{title: 'Title',subtitle: 'SubTitle',},],},],},{name: 'chapter2',sections: [{name: 'section1',questions: [{title: 'Title',subtitle: 'SubTitle',},{title: 'Title',subtitle: 'SubTitle',},],},{name: 'section2',questions: [{title: 'Title',subtitle: 'SubTitle',},{title: 'Title',subtitle: 'SubTitle',},],},],},],},{id: 2,subject: 'Subject',chapters: [{name: 'chapter1',sections: [{name: 'section1',questions: [{title: 'Title',subtitle: 'SubTitle',},{title: 'Title',subtitle: 'SubTitle',},],},{name: 'section2',questions: [{title: 'Title',subtitle: 'SubTitle',},{title: 'Title',subtitle: 'SubTitle',},],},],},{name: 'chapter2',sections: [{name: 'section1',questions: [{title: 'Title',subtitle: 'SubTitle',},{title: 'Title',subtitle: 'SubTitle',},],},{name: 'section2',questions: [{title: 'Title',subtitle: 'SubTitle',},{title: 'Title',subtitle: 'SubTitle',},],},],},],},];

const result = arr1.flatMap(({chapters}) => 
    chapters.flatMap(({sections}) => 
        sections.flatMap(({questions}) => questions)
    )
);

console.log(result);