code: function MathFormula() {
          this.addInput("x", "number");
          this.addInput("y", "number");
          this.addOutput("", "number");
          this.properties = { x: 1.0, y: 1.0, formula: "x+y" };
          this.code_widget = this.addWidget(
              "text",
              "F(x,y)",
              this.properties.formula,
              function(v, canvas, node) {
                  node.properties.formula = v;
              }
          );
          this.addWidget("toggle", "allow", LiteGraph.allow_scripts, function(v) {
              LiteGraph.allow_scripts = v;
          });
          this._func = null;
      }
docs: math library for safe math operations without eval