How to use the blockly.Field function in blockly

Blockly.Events.fire(new Blockly.Events.Change(
        this.sourceBlock_, 'field', this.name, oldValue, newValue));
    }
  }
  manageEvent();
  if (noGroup) {
    Blockly.Events.setGroup(false);
  }
};

/**
 * By default there is no difference between the human-readable text and
 * the language-neutral values.  Subclasses (such as dropdown) may define this.
 * @param {string} newText New text.
 */
Blockly.Field.prototype.setValue = function(newText) {
  if (newText === null) {
    // No change if null.
    return;
  }
  var oldText = this.getValue();
  if (oldText == newText) {
    return;
  }
  var that = this;
  this.fieldHasChanged(oldText, newText, function() {
    that.setText(newText);
  });
};

/**
 * Set the checkbox to be checked if strBool is 'TRUE', unchecks otherwise.

*/
var FieldTable = function(data, opt_extraColumns, hideHeaders) {
  FieldTable.constructor.call(this, '');
  // Set the initial state.
  // this.setValue(json);
  this.width_ = 0;
  this.height_ = 0;
  this.size_ = { width: this.width_, height: this.height_ };
  this.data_ = data;
  this.extraColumns_ = opt_extraColumns ? opt_extraColumns : {
    varNames: [],
    mappings: {}
  };
  this.showHeaders = !hideHeaders;
};
FieldTable.prototype = Object.create(Blockly.Field.prototype);
FieldTable.prototype.constructor = FieldTable;

FieldTable.NO_PATTERN = 0;
FieldTable.CLASS_PATTERN = 1;
FieldTable.PROPERTY_PATTERN = 2;

FieldTable.PATTERN_LABEL = 'pattern';

/**
 * Editable fields are saved by the XML renderer, non-editable fields are not.
 */
FieldTable.prototype.EDITABLE = false;

FieldTable.prototype.setEventBindingsForBlock_ = function(block) {
  if (block) {
    var root = block.getSvgRoot();

Blockly.FieldVariable.prototype.dispose = function() {
  var varName = this.getValue();
  var block = this.sourceBlock_;
  var workspace = this.workspace_;
  Blockly.Field.prototype.dispose.call(this);
  this.workspace_ = null;
  var defaultVarNames = workspace && defaultVarNamesByWorkspace[workspace];
  if (block && varName && workspace
      && defaultVarNames
      && defaultVarNames.indexOf(varName) != -1
      && workspace.getVariableUses(varName).length == 0) {
    workspace.deleteVariable(varName);
  }
};

}
    morphShadowRec(this);
  }
  manageEvent();
  if (noGroup) {
    Blockly.Events.setGroup(false);
  }
};

/**
 * When a field changes, generate event and manage shadow state.
 * @param {Object} oldValue The old field value
 * @param {Object} newValue The new field value
 * @protected
 */
Blockly.Field.prototype.fieldHasChanged = function(oldValue, newValue, manageEvent) {
  var noGroup = false;
  if (this.sourceBlock_) {
    if (true /*this.sourceBlock_.workspace.options.shadowMorphEnabled*/ &&
        Blockly.Events.recordUndo) {
      if (Blockly.Events.isEnabled()) {
        noGroup = true; //!Blockly.Events.getGroup();
        if (noGroup) {
          Blockly.Events.setGroup(true);
        }
      }
      morphShadowRec(this.sourceBlock_);
    }
    if (Blockly.Events.isEnabled()) {
      Blockly.Events.fire(new Blockly.Events.Change(
        this.sourceBlock_, 'field', this.name, oldValue, newValue));
    }