missing values - fill empty array slots-CodePudding

Hi Community I struggle to understand the following behavior. Its a typicall Monday problem. All I want is to fill the empty array slots with the integer 0.

myArray = [
  [1, ,1, ],
  [ , ,1, ],
  [ , ,1, ],
  [1, , , ],
]
      
for (var a = 0; a < myArray.length; a  ) {
  for (var b = 0; b < myArray[a].length; b  ) {
    if (myArray[a][b] == undefined) {
        myArray[a][b] = 0
    }
  }
  console.log("myArray["   a   "]["  b  "]"   " = "   myArray[a][b])
}

CodePudding user response：

You are trying to access b outside the loop

Just move it to the loop

myArray = [
  [1, , 1, ],
  [, , 1, ],
  [, , 1, ],
  [1, , , ],
]

for (var a = 0; a < myArray.length; a  ) {
  for (var b = 0; b < myArray[a].length; b  ) {
    if (myArray[a][b] == undefined) {
      myArray[a][b] = 0
    }
    console.log("myArray["   a   "]["   b   "]"   " = "   myArray[a][b])
  }
}

Also, better never use var:

myArray = [
  [1, , 1, ],
  [, , 1, ],
  [, , 1, ],
  [1, , , ],
]

for (let a = 0; a < myArray.length; a  ) {
  for (let b = 0; b < myArray[a].length; b  ) {
    if (myArray[a][b] == undefined) {
      myArray[a][b] = 0
    }
  }
  console.log("myArray["   a   "]["   b   "]"   " = "   myArray[a][b])
}

If you would use let you will get an error without debugging

CodePudding user response：

Another way to fill-in empty values with zerro

const myArray = [
  [1, ,1, ],
  [ , ,1, ],
  [ , ,1, ],
  [1, , , ],
];

const filled = myArray.map(level1 => [...level1].map(value => value ? value : 0));

console.log(filled);

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

CodePudding user response：

The OP code was logging values within the outer loop which is out of scope of b which was defined within the inner loop. Log properties right after they are defined which in your case should be the inner loop.

const arrArrs = [
  [ 1, '',  1, '' ],
  [ '', '', 1, '' ],
  [ '', '', 1, '' ],
  [ 1, '', '', '' ]
];

for (let a = 0; a < arrArrs.length; a  ) {
  for (let b = 0; b < arrArrs[a].length; b  ) {
    if (arrArrs[a][b] != '') {
      console.log(`arrArrs[${a}][${b}] = ${arrArrs[a][b]}`);
      continue;
    }
    arrArrs[a][b] = 0;
    console.log(`arrArrs[${a}][${b}] = ${arrArrs[a][b]}`);
  }
}
console.log(JSON.stringify(arrArrs));