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Tolerim
21 hours ago

How can I resolve the issue of undefined values being passed into a function that is declared in a separate JavaScript file and utilized within a React component?

The given text includes a JavaScript file called "test.js" that contains a function called "a" which logs the given data to the console. Additionally, there is a functional component called "File.js" that imports the "a" function from "test.js" and calls it using the useEffect hook. The expected output is "hello," but the actual output is "undefined." There is confusion about the issue, and the solution is being sought. Here's the modified paragraph with HTML tags and rephrased question: There is a JavaScript file named "test.js" that houses a function called "a." The function logs a given data to the console. Along with this, there is a functional component named "File.js," which imports the "a" function from "test.js" and calls it with the useEffect hook. However, instead of getting "hello" in the console, the output reads "undefined." Can you help me understand what is causing this problem? Here is the code:

<script language="javascript">
  export const a =(data)=>{
    console.log(data)
  }
</script>

<script langauge="javascript">
  import React, {useEffect} from "react";
  import {a} from "./test";

  let data = "hello"

  function File() {
    useEffect(()=> {a(data)},[]}
    return (<div>something</div>)
  }

  export default File;
</script>
I hope this helps! Let me know if you have any other questions.
Answers(1)
avatar
Tolerim
21 hours ago
Verified Answer
The issue here is that the function a() is being called before data is defined. When the component mounts, the useEffect hook runs and calls the a() function with the value of data. However, at the time of running the useEffect hook, data is still undefined. To fix this issue, you should move the declaration of data to inside the File() component, so that it is defined before it is passed to the a() function. Here is an updated version of the File.js file: 
import React, { useEffect } from "react";
import { a } from "./test";

function File() {
  let data = "hello";

  useEffect(() => {
    a(data);
  }, []);

  return <div>something</div>;
}

export default File;
In this example, data is defined within the File component before being passed to the a() function. Now when the component mounts, a() is called with the value of data, which is "hello". This will log "hello" to the console.
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