获取对象数组内数组的累积长度

Question

I have been searching for quite a while but cannot find an answer to my issue. The problem is pretty simple; I have an array of objects, each containing another array of objects. I want to get the cumulative length of all arrays inside all objects.

Here is some sample data:

const items = [
    {
        id: 1,
        title: "Test 1",
        data: [
            {
                ...
            },
            {
                ...
            },
        ]
    },
    {
        id: 2,
        title: "Test 2",
        data: [
            {
                ...
            },
        ]
    }
]

In this sample, the length should be 3 since there is 2 objects inside the first object's data property and 1 object inside the second object's data property.

Answer 1

pretty simple

 const items = [ { id: 1, title: "Test 1", data: [{a:1},{a:1} ] }, { id: 2, title: "Test 2", data: [{a:1},{a:1},{a:1},{a:1}] } ] console.log('cumulative length ', items.reduce((a,c)=>a+c.data.length,0) )

Answer 2

All you need to do is loop through all items you got, check the length of the data array of each item and add that length to a variable. Here is a working snippet:

 const items = [ { id: 1, title: "Test 1", data: [ { }, { }, ] }, { id: 2, title: "Test 2", data: [ { }, ] } ]; // Initialize the count variable as 0 var count = 0; // Pass through each item items.forEach((item)=>{ // Adding the count of data of each item count += item.data.length; }); // Outputting the count console.log(count);

Answer 3

If you want to use for of loop that works too.

const countObjects = (arrayInput) => {
  let totalCount = 0
  for(let item of items) {
    totalCount += item.data.length
  }
  return totalCount
}
console.log(countObjects(items))