text: Blockly.Blocks['clear'] = {
      init: function() {
        this.appendValueInput("logString")
            .setCheck("String")
            .setAlign(Blockly.ALIGN_RIGHT)
            .appendField("clear");
        this.setPreviousStatement(true, null);
        this.setNextStatement(true, null);
        this.setColour(165);
     this.setTooltip("clear the screen");
     this.setHelpUrl("");
      }
    };
    
    Blockly.JavaScript['clear'] = function(block) {
      const code ='clearCanvas();\n';
      return code;
    }