Adds iteration and simpler filtering to DataTable and DataView objects.

gviz-ext.js

const extendGoogleVisualization = () => {
  const dataView = google.visualization.DataView.prototype;
  const dataTable = google.visualization.DataTable.prototype;
  dataView.getNiceRow = dataTable.getNiceRow = function(r) {
    const row = [];
    for (let c = 0; c < this.getNumberOfColumns(); ++c) {
      const colId = this.getColumnId(c);
      row.push(this.getValue(r, c));
      if (colId) {
        row[colId] = row[c];
      }
    }
    return row;
  };

  dataView[Symbol.iterator] = dataTable[Symbol.iterator] = function() {
    const self = this;
    return {
      _row: -1,
      next() {
        const done = ++this._row >= self.getNumberOfRows();
        return {
          done: done,
          value: done ? null : self.getNiceRow(this._row),
        };
      },  
    };
  };

  dataView.filter = dataTable.filter = function(filter) {
    const rows = [...this].reduce((rows, row, i) => {
      return rows.concat(filter(row) ? [i] : []);
    }, []);
    const dataView = new google.visualization.DataView(this);
    dataView.setRows(rows);
    return dataView;
  };

  dataView.filterByColumn = dataTable.filterByColumn = function(...filters) {
    const convertToFilterObject = (filter, colIndex) => {
      const filterType = typeof filter;
      switch (filterType) {
        case 'string':
        case 'number':
        case 'function':
          return {
            column: colIndex,
            value: filter,
          };
        case 'object':
          if (filter instanceof RegExp) {
            return {
              column: colIndex,
              test: v => filter.test(v),
            };
          } else if (filter instanceof Array) {
            if ('number' == typeof filter[1]) {
              // [min, max]  NOTE: Does not work for specifying column and number value filter.
              return {
                column: colIndex,
                minValue: filter[0],
                maxValue: filter[1],
              };
            } else {
              // [column, filter]
              return Object.assign(convertToFilterObject(filter[1]), {
                column: filter[0],
              });
            }
          } else {
            return filter;
          }
        default: throw 'Unsupported filter';
      }
    };
    const filterObjects = filters.map(convertToFilterObject).filter(f => !!f);
    const dataView = new google.visualization.DataView(this);
    dataView.setRows(this.getFilteredRows(filterObjects));
    return dataView;
  };
};

const onLoadCallback = () => {
  console.log('loaded');
  const data = google.visualization.arrayToDataTable([
    [{id: 'n', label: 'name'}, 'foo', {id: 'bar'}],
    ['tom', 1, 2],
    ['pam', 1, 2],
    ['jan', 2, 3],
  ]);
  extendGoogleVisualization();
  console.log(
      data.getNiceRow(0),
      [...data.filterByColumn(null, null, /3/).filterByColumn({column: 0, value: 'jan'})],
      [...data.filter(row => row.bar == 2).filter(row => /tom/.test(row[0]))]);
};

google.charts.load('current', {packages: ['corechart']});
google.charts.setOnLoadCallback(onLoadCallback);