Nodejs SyntaxError: Unexpected identifier when adding function keyword

Question

I am new to nodejs and JavaScript. I am writing automation framework using pageobject model using webdriver.io v5. I am facing two issues and would appreciate some clarification.

****************** Question 1 ******************
I have the following format code which works fine but returns Undefined as return value in main class

class ABC.js
***************
class ABC {
   constructor() {};
   extractCode() {
     return (1 > 2).valueOf();// I am expecting false as output
   }
}
module.exports = ABC;
*********** class D.js *******

var ABC = require('ABC');
class D extends ABC {
   const abc = new ABC();
   console.log(abc.extractCode());// I get undefined
}
************** Question 2 ************
    class ABC.js
    ***************
    class ABC {
       constructor() {};
       function extractCode() {
         return (1 > 2).valueOf();// I am expecting false as output
       }
    }
    module.exports = ABC;

I get the following error :

function extractCode() {
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

SyntaxError: Unexpected identifier

Why is adding function keyword throwing error on JavaScript?

You're not closing the Function

nanquim
– nanquim

2020-03-13 03:28:16 +00:00
Commented Mar 13, 2020 at 3:28 — nanquim
– nanquim, Commented Mar 13, 2020 at 3:28
@tramada Updated the code. Thanks for letting me know

ChanChow
– ChanChow

2020-03-13 03:47:08 +00:00
Commented Mar 13, 2020 at 3:47 — ChanChow
– ChanChow, Commented Mar 13, 2020 at 3:47

ray · Accepted Answer · 2020-03-13 03:58:24Z

2

Question 1:

return (1 > 2).valueOf();// I am expecting false as output

Just return 1 > 2;. The expression already evaluates to a boolean value. No need for valueOf().

Question 2:

You're declaring a method on a class. So this is valid:

class A {
  extractCode () {
   // do stuff
  }
}

But what you're doing in your code is trying to declare a freestanding function in the context of a class definition, which isn't valid js.

Observation

Why are you instantiating ABC inside a class that extends ABC?

class D extends ABC {
   const abc = new ABC(); // why?
   console.log(abc.extractCode());// I get undefined
}

class ABC {
  extractCode () {
    return 1 > 2;
  }
}

class DEF extends ABC {} // inherits extractCode from ABC

class GHI extends DEF {
  extractCode () { // override to change the subclass behavior
    return 'bananas';
  }
}

const abc = new ABC();
console.log(abc.extractCode()); // false

const def = new DEF();
console.log(def.extractCode()); // false

const ghi = new GHI();
console.log(ghi.extractCode()); // bananas

These questions are more about fundamental javascript syntax than all the technologies you tagged it with. This has nothing at all to do with jquery, node.js, reactjs, or angular-fullstack.

Read up on the basics of javascript.

edited Mar 13, 2020 at 3:58

answered Mar 13, 2020 at 3:31

ray

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2 Comments

ChanChow Over a year ago

I tried that return 1 >2 and I get Undefined on main class

ChanChow Over a year ago

I am still learning class patters in JS. I am from Java background. But to answer your question on why I am using class declaration, I need to use the methods from ABC into class D which should give me value false. I have declared require('ABC') before the class definition of D and instantiated ABC inside class D. I know this might be wrong, still trying to learn.

brycelikesdogs · Accepted Answer · 2020-03-13 03:28:26Z

0

For question 2: It should just be extractCode(){}, remove the function keyword. This is because you don't need it when declaring class methods. Also add a closing bracket.

Try this:

    class ABC {
       constructor() {};
       extractCode() {
         return (1 > 2).valueOf();
       }
    }
    module.exports = ABC;

answered Mar 13, 2020 at 3:28

brycelikesdogs

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