JavaScript: The variable `scopes` is declared

Question

JavaScript: The variable `scopes` is declared

I'm completely new to JavaScript. Can anyone help me understand why this code isn't working, and what changes I need to make to fix it?

function getResults(keywords) {

        foo.foo = function() {
               var bar = foo.getSomeText; // Contains "blabla"
        };

        return bar;

    }

    // Global scope

    alert(bar); // Does nothing

Edit (apologies for the lack of information):

The issue is that I am trying to retrieve text from an XHR request and I need to use a function to handle the onreadystatechange event. Here is the original code:

function getResults(keywords) {
     // Make a request and get results

    var xhr = new XMLHttpRequest();
    xhr.open('GET', './autoc.php?s='+ encodeURIComponent(keywords));

    xhr.onreadystatechange = function() {
        if (xhr.readyState == 4 && xhr.status == 200) {
           var response = xhr.responseText;
          var test = response.split('|');

        }
    };

    xhr.send(null);

    return test;

}

var hum = getResults('test');
console.log(hum);

javascript scope

Answer 1

Answer №1

This solution should do the trick.

let result;
const data = {content: 'example'};

function fetchResults(searchTerm) {

    data.response = (function() {
        return result = data.content; // Contains "example"
    })();

    return result;

}

// Global scope
result = fetchResults('hello');

console.log(result); // Nothing will happen

JSFiddle Demo

Your original code may not work due to a syntax error since 'result' is not declared.
'data' is an object here and also needs to be initialized before use.
fetchResults returns 'result', which can only be accessed after executing the function and assigning it to a global variable.

UPDATE

AJAX calls are asynchronous, so attempting to retrieve the value from the function that is being set in the callback will not work properly. Since the request is asynchronous, the function has already returned before the callback is executed. Therefore, the 'test' variable will always be undefined in this scenario.

Answer 2

This solution should do the trick.

let result;
const data = {content: 'example'};

function fetchResults(searchTerm) {

    data.response = (function() {
        return result = data.content; // Contains "example"
    })();

    return result;

}

// Global scope
result = fetchResults('hello');

console.log(result); // Nothing will happen

JSFiddle Demo

Your original code may not work due to a syntax error since 'result' is not declared.
'data' is an object here and also needs to be initialized before use.
fetchResults returns 'result', which can only be accessed after executing the function and assigning it to a global variable.

UPDATE

AJAX calls are asynchronous, so attempting to retrieve the value from the function that is being set in the callback will not work properly. Since the request is asynchronous, the function has already returned before the callback is executed. Therefore, the 'test' variable will always be undefined in this scenario.

Answer 3

Answer №2

foo.foo = function() {
    var example = foo.retrieveText; // Contains "blahblah"
};
return example;

Despite the absence of declaration for foo, the variable example is defined within a function and therefore has local scope in JavaScript. It cannot be accessed outside of this function, making it impossible to return it as attempted here.

If you wish to return example, it must be declared outside of the function:

var example = foo.retrieveText; // Contains "blahblah"
foo.foo = function() {

};
return example;

Answer 4

foo.foo = function() {
    var example = foo.retrieveText; // Contains "blahblah"
};
return example;

Despite the absence of declaration for foo, the variable example is defined within a function and therefore has local scope in JavaScript. It cannot be accessed outside of this function, making it impossible to return it as attempted here.

If you wish to return example, it must be declared outside of the function:

var example = foo.retrieveText; // Contains "blahblah"
foo.foo = function() {

};
return example;

Answer 5

Answer №3

In JavaScript, the extent of a variable is quite straightforward. It falls into one of two categories:

The function in which it is initially declared
The global scope (referred to as window in a browser) if it is not declared within a specific function

Answer 6

In JavaScript, the extent of a variable is quite straightforward. It falls into one of two categories:

The function in which it is initially declared
The global scope (referred to as window in a browser) if it is not declared within a specific function

Answer 7

Answer №4

The location where a variable is declared determines its scope. If you declare a variable inside the script tag directly, as opposed to within a method within the script tag block, it will become a global variable.

It seems unclear what your intention is with the code snippet provided, especially because the first "foo" in "foo.foo" is not defined. You may want to consider using this alternative approach:

<script type="text/javascript">
var foo = {} // create an empty global object named 'foo'

foo.foo = function() {
    var bar = "some random text";

//// additional code goes here

return bar;

}

var myBar = foo.foo(); // retrieve text from the method. Remember that the method call should come after the method definition
alert(myBar);
</script>

Learning Javascript can be enjoyable and straightforward. I recommend exploring introductory texts and studying code examples for better understanding.

Answer 8

The location where a variable is declared determines its scope. If you declare a variable inside the script tag directly, as opposed to within a method within the script tag block, it will become a global variable.

It seems unclear what your intention is with the code snippet provided, especially because the first "foo" in "foo.foo" is not defined. You may want to consider using this alternative approach:

<script type="text/javascript">
var foo = {} // create an empty global object named 'foo'

foo.foo = function() {
    var bar = "some random text";

//// additional code goes here

return bar;

}

var myBar = foo.foo(); // retrieve text from the method. Remember that the method call should come after the method definition
alert(myBar);
</script>

Learning Javascript can be enjoyable and straightforward. I recommend exploring introductory texts and studying code examples for better understanding.

JavaScript: The variable `scopes` is declared

Answer №1

Answer №2

Answer №3

Answer №4

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