feat: create a JS helpers class (#190)

* feat: create js helpers

* capture arrow functions

* make everything more readable

lib/__fixtures__/curriculum-helpers-javascript.ts

@@ -56,6 +56,15 @@ myFunc();
 */
 `;
 
+const functionDeclaration =
+  "function myFunction(param1, param2 = 'default', param3) {";
+const constFunction =
+  "const myFunction = (param1, param2 = 'default', param3) => {";
+const letFunction =
+  "let myFunction = function(param1, param2 = 'default', param3) {";
+
+const arrowFunction = `const myFunc = name => console.log("Name")`;
+
 const testValues = {
   jsCodeWithSingleAndMultLineComments,
   jsCodeWithSingleAndMultLineCommentsRemoved,
@@ -65,6 +74,10 @@ const testValues = {
   jsCodeWithNoArgCall,
   jsCodeWithArgCall,
   jsCodeWithCommentedCall,
+  functionDeclaration,
+  constFunction,
+  letFunction,
+  arrowFunction,
 };
 
 export default testValues;

lib/__tests__/javascript-helper.test.ts

@@ -0,0 +1,36 @@
+import jsTestValues from "../__fixtures__/curriculum-helpers-javascript";
+
+import { getFunctionParams } from "../index";
+
+const { functionDeclaration, constFunction, letFunction, arrowFunction } =
+  jsTestValues;
+
+describe("js-help", () => {
+  describe("getFunctionArgs", () => {
+    it("gets arguments from function declarations", function () {
+      const parameters = getFunctionParams(functionDeclaration);
+      expect(parameters[0].name).toBe("param1");
+      expect(parameters[1].defaultValue).toBe("default");
+      expect(parameters[1].name).toBe("param2");
+      expect(parameters[2].name).toBe("param3");
+    });
+    it("gets arguments from const function variables", function () {
+      const parameters = getFunctionParams(constFunction);
+      expect(parameters[0].name).toBe("param1");
+      expect(parameters[1].defaultValue).toBe("default");
+      expect(parameters[1].name).toBe("param2");
+      expect(parameters[2].name).toBe("param3");
+    });
+    it("gets arguments from let function variables", function () {
+      const parameters = getFunctionParams(letFunction);
+      expect(parameters[0].name).toBe("param1");
+      expect(parameters[1].defaultValue).toBe("default");
+      expect(parameters[1].name).toBe("param2");
+      expect(parameters[2].name).toBe("param3");
+    });
+    it("gets arguments from arrow functions", function () {
+      const parameters = getFunctionParams(arrowFunction);
+      expect(parameters[0].name).toBe("name");
+    });
+  });
+});

lib/index.ts

@@ -352,3 +352,47 @@ export class CSSHelp {
     return [...new Set(allSelectors)];
   }
 }
+
+/**
+ * Extracts all function parameters and default values from a function
+ * @param functionObject A function in string form
+ * @returns {{name:String,defaultValue: String | undefined}}
+ */
+export function getFunctionParams(code: string) {
+  // Regular expression to match function declarations, arrow functions, and function expressions
+  const functionDeclareRegex = /(?:function\s*[^(]*\(([^)]*)\))/;
+
+  const functionVariableRegex =
+    /(?:\b(?:const|let|var)\s*\w+\s*=\s*(?:function)?\s*\(([^)]*)\))/;
+
+  const arrowFunctionRegex = /=\s+([^)]*)=>/;
+
+  // Match the function parameters
+  const paramMatch =
+    code.match(functionDeclareRegex) ||
+    code.match(functionVariableRegex) ||
+    code.match(arrowFunctionRegex);
+
+  if (paramMatch) {
+    // Find the captured group containing the parameters
+    const paramString =
+      paramMatch[1] || paramMatch[2] || paramMatch[3] || paramMatch[4];
+    // Split the parameter string by commas to get individual parameters
+    const params = paramString.split(",").map((param: string) => {
+      // Split each parameter by '=' to separate name and default value
+      const parts = param.trim().split("=");
+      // If the parameter has a default value, extract it, otherwise set it to undefined
+      const defaultValue =
+        parts.length > 1 ? parts[1].replace(/['"]/g, "").trim() : undefined;
+      // Return an object with the parameter name and default value
+      return {
+        name: parts[0].trim(),
+        defaultValue: defaultValue,
+      };
+    });
+    return params;
+  }
+
+  // Return an empty array if no function parameters are found
+  return [];
+}