Is there a way to execute a JavaScript string as some functions? I'm using eval but it is not working

Question

Is there a way to execute a JavaScript string as some functions? I'm using eval but it isn't working.

I'm trying this as I need to read values from a YML file for my serenity js test.

This is what I'm trying to do

this.data = "element1.element2" 
this.test1 = "safeLoad(readFileSync(`config/${this.fileName}.yml`, 'utf8'))";
console.log(this.test1)
console.log(`${this.test1}.${this.data}`);

And this is how I'm trying to execute the string

eval(`${this.testabc}.${this.data}`)

However, when I execute this, I'm having the following error:

ReferenceError: safeLoad is not defined

P.S.: If I execute the code normally (without eval) it works fine!

safeLoad(readFileSync(`config/${this.fileName}.yml`, 'utf8')).element1.element2

Does anyone know how to execute code like that as a string?

It's a scoping issue. You should probably check [How does the “this” keyword work?](https://stackoverflow.com/questions/3127429/how-does-the-this-keyword-work) and [JavaScript Scope](https://www.w3schools.com/js/js_scope.asp). Since it's impossible to know what `this` actually stands for within your question, all I can say with certainty is that it's looking for the `safeLoad` function in the wrong scope. — icecub, Dec 29 '19 at 13:53
There are lots of reasons why not to do this (security), however I suspect safeLoad is out of scope for eval, check https://stackoverflow.com/questions/9781285/specify-scope-for-eval-in-javascript — James, Dec 29 '19 at 13:56

score 0 · Accepted Answer · answered Dec 29 '19 at 14:02

I guess you import safeLoad using es6 syntax.

If yes, when you use babel to transpile code, safeLoad will be omitted. Because the transpiler though that safeLoad will not be used on your code.

To understand, please check the bellowing picture, or this babel example.

To fix this, you should use require instead of import(es6):

// instead of
import safeLoad from 'safeLoad'
// use this:
const safeLoad = require('safeLoad').default

// instead of
import { safeLoad } from 'safeLoad'
// use this:
const { safeLoad } = require('safeLoad')

Is there a way to execute a JavaScript string as some functions? I'm using eval but it is not working

1 Answers1