Find islands in Boolean Matrix

Matrix.js

class Matrix {
  constructor(n, m) {
    this.numrows = n;
    this.numcolumns = m;
    this.generateMatrix();
  }

  generateMatrix() {
    var rows = [];
    for (var j = 0; j < this.numrows; j++) {
      var columns = [];
      for (var i = 0; i < this.numcolumns; i++) {
        columns.push({
          val: Math.round(Math.random()),
          visited: false
        });
      }
      rows.push(columns);
    }
    this.data = rows;
   }
 }