My friend CM's JavaScript version of calculating max rectangle area

MaxRectangleFinder.js

const f = a => {
  let max = 0;
  const getLocalMax = a => {
    let localMax = 0, maxJ = a[0].length -1;
  
    const reset = i => {
      const size = (i+1)*(maxJ+1);
      if(size > localMax) 
        localMax = size;
    }
  
    a.some( (row, i) => {
      row.split('').some( (data, j) => {
        if(j > maxJ) 
            return true;
        if(!+data) {
          maxJ = j - 1;
          return true;
        }
      });
      reset(i);
    });
    return localMax;
  };

  a.forEach( (row, i) => {
    row.split('').forEach( (_, j) => {
      const currentArr = a.slice(i).map( r => r.slice(j) );
      let localMax = getLocalMax( currentArr );
      if(localMax > max) 
        max = localMax;
    })
  });
  return max;
};

var matrices = [
    [
        "1111",
        "0110",
        "1110",
        "1111"
    ],
    [
        "11011",
        "01101",
        "11110",
        "11111",
        "01111"
    ],
    [
        "101101",
        "111111",
        "011111",
        "111111",
        "001111",
        "011111"
    ]
];

for (var i = 0; i < matrices.length; i++) {
    var matrix = matrices[i];
    var maxArea = f(matrix);
    console.log("The max area is " + maxArea);
}