如何动态构建一个javascript对象并在嵌套循环中推入数组？

Question

I'm trying to dynamically build Objects and push them one by one into an Array.

My code so far is this:

matrix([[0,1,1], [1,00], [1,1,1])

const matrix = (sequence) => {
   const rows = {}
   const rowsAry = []
   let row
   let idx
  
   for (let i=0; i < samples.length; i++) {
       row = `row${i}`
    
       for (let j=0; j < samples[i].length; j++) {
          if (samples[i][j] === 1) {
               idx = []
               rows[row] = rows[row] + 1 || 1 
               rows['indeces'] = idx.push(j)  
               rowsAry.push(rows)
            }
            
        }
    }
    console.log(rowsAry)

}

This obviously isn't working. I'm trying to map out all the '1's' in the sequence and know how many are in a row and what there indices are.

The wrong out put is:

[ { row0: 3, indeces: 1, row1: 2, row2: 2 },
  { row0: 3, indeces: 1, row1: 2, row2: 2 },
  { row0: 3, indeces: 1, row1: 2, row2: 2 },
  { row0: 3, indeces: 1, row1: 2, row2: 2 },
  { row0: 3, indeces: 1, row1: 2, row2: 2 },
  { row0: 3, indeces: 1, row1: 2, row2: 2 },
  { row0: 3, indeces: 1, row1: 2, row2: 2 },
  { row0: 3, indeces: 1, row1: 2, row2: 2 },
  { row0: 3, indeces: 1, row1: 2, row2: 2 } ]

Hoped for output would be:

[{row1: 2, indices: [1,2]}, 
 {row2: 1, indices: [0]}, 
 {row3: 3, indices: [0,1,2]}
] 

Answer 1

You need to create a new object each time through the outer loop. And only push it onto rowsAry once, not each time through the inner loop.

 const matrix = (samples) => { const rowsAry = [] for (let i = 0; i < samples.length; i++) { let row = `row${i}` let indices = []; for (let j = 0; j < samples[i].length; j++) { if (samples[i][j] === 1) { indices.push(j); } } rowsAry.push({[row]: indices.length, indices: indices}); } console.log(rowsAry) } matrix([ [0, 1, 1], [1, 00], [1, 1, 1] ])

Answer 2

You can solve it by simply using array map and forEach method. Traverse the array of arrays and check for ones to the inside array by using array forEach method and if found put it to the resultant array. At last, using the resultant array make your required object.

 const matrix = (sequence) => { return sequence.map((x, i) => { const ret = []; x.forEach((y, j) => { if (y === 1) ret.push(j); }); const key = `row${i + 1}`; const obj = { [key]: ret.length, indices: ret }; return obj; }); }; const ret = matrix([ [0, 1, 1], [1, 0, 0], [1, 1, 1], ]); console.log(ret);

Answer 3

Or nested reduce() calls...

 const matrix = (sequence) => { return sequence.reduce((a, r, i) => { indices = r.reduce((ra, rn, ri) => { if (rn === 1) ra.push(ri); return ra; }, []); a.push({[`row${i}`]: indices.length, indices: indices}); return a; }, []); } console.log(matrix([[0,1,1], [1,0,0], [1,1,1]]))

But in reference to Barmar's comment about using different rowX keys a more accessible shape for your objects might look something along the lines of

{row: 1, count: 2, indices: [1, 2]}