Seeking assistance with producing results

Question

Seeking assistance with producing results

Is there someone who can provide an answer?

What will be the output of the code snippet below when logged to the console and why?

(function(){    
      var a = b = 3;    
    })();
    console.log("Is 'a' defined? " + (typeof a !== 'undefined'));    
    console.log("Is 'b' defined? " + (typeof b !== 'undefined'));

What do you expect the following code block to print to the console, and what is the reason behind it?

var myObject = { 
        foo: "bar",    
        func: function() {    
            var self = this;    
            console.log("outer func:  this.foo = " + this.foo);    
            console.log("outer func:  self.foo = " + self.foo);    
            (function() {    
                console.log("inner func:  this.foo = " + this.foo);   
                console.log("inner func:  self.foo = " + self.foo); 
            }());    
        }    
    };    
    myObject.func();

javascript typescript

Answer 1

Answer №1

The initial segment of your script is essentially the same as this.

(function(){
  var a;
  b = 3;
  a = b;
})();

console.log("Is 'a' defined? " + (typeof a !== 'undefined'));

console.log("Is 'b' defined? " + (typeof b !== 'undefined'));

In this example, variable a is declared within the immediate function's scope and thus remains unrecognized beyond that scope, resulting in it being undefined externally. However, variable b is established as a global variable, enabling visibility throughout and preventing it from being undefined; its value is 3.

Regarding the concluding portion of code, each function operates within its individual context to which this pertains. For primary-level functions, commonly known as methods in certain coding languages, this denotes the current object it belongs to. Though for an internal function nested within func, it retains a distinct context dictating what this signifies. As a result, this refers to undefined rather than the designated object. Yet utilizing an alternative variable like self, defined at an upper scope of that function, grants access to external variables. The distinctive aspect lies with the name-specific variable this. This holds significance.

var myObject = { 
    foo: "bar",    
    func: function() {    
        var self = this;    
        console.log("outer func:  this.foo = " + this.foo);    
        console.log("outer func:  self.foo = " + self.foo);    
        (function() {    
            console.log("inner func:  this.foo = " + this.foo);   
            console.log("inner func:  self.foo = " + self.foo); 
        }());    
    }    
};    
myObject.func();

Answer 2

The initial segment of your script is essentially the same as this.

(function(){
  var a;
  b = 3;
  a = b;
})();

console.log("Is 'a' defined? " + (typeof a !== 'undefined'));

console.log("Is 'b' defined? " + (typeof b !== 'undefined'));

In this example, variable a is declared within the immediate function's scope and thus remains unrecognized beyond that scope, resulting in it being undefined externally. However, variable b is established as a global variable, enabling visibility throughout and preventing it from being undefined; its value is 3.

Regarding the concluding portion of code, each function operates within its individual context to which this pertains. For primary-level functions, commonly known as methods in certain coding languages, this denotes the current object it belongs to. Though for an internal function nested within func, it retains a distinct context dictating what this signifies. As a result, this refers to undefined rather than the designated object. Yet utilizing an alternative variable like self, defined at an upper scope of that function, grants access to external variables. The distinctive aspect lies with the name-specific variable this. This holds significance.

var myObject = { 
    foo: "bar",    
    func: function() {    
        var self = this;    
        console.log("outer func:  this.foo = " + this.foo);    
        console.log("outer func:  self.foo = " + self.foo);    
        (function() {    
            console.log("inner func:  this.foo = " + this.foo);   
            console.log("inner func:  self.foo = " + self.foo); 
        }());    
    }    
};    
myObject.func();

Answer 3

Answer №2

First Code:

(function(){    
  var a = b = 3;    
})();
console.log("a defined? " + (typeof a !== 'undefined'));    
console.log("b defined? " + (typeof b !== 'undefined'));

Output:

a defined? false
b defined? true

Description: In this code snippet, an Immediately Invoked Function Expression (IIFE) is used. Variable a is declared inside the function's scope while variable b is not declared and therefore becomes part of the global scope. When trying to access these variables outside the function, a is undefined but b is defined.

Second Code:

var myObject = { 
   foo: "bar",    
   func: function() {    
       var self = this;    
       console.log("outer func:  this.foo = " + this.foo);    
       console.log("outer func:  self.foo = " + self.foo);    
       (function() {    
           console.log("inner func:  this.foo = " + this.foo);   
           console.log("inner func:  self.foo = " + this.foo); 
       }());    
   }    
};    
myObject.func();

Output:

outer func:  this.foo = bar
outer func:  self.foo = bar
inner func:  this.foo = undefined
inner func:  self.foo = bar

Description:

The important concept here is the usage of this reference inside a function. When it refers to an object's property within that object's method, it simply refers to the object itself. The first two logs show the expected result. However, when an IIFE is used, this now refers to the global object (Window object), hence resulting in undefined. On the other hand, using self within the inner function retains the value of foo from the object, providing the expected output.

Answer 4

First Code:

(function(){    
  var a = b = 3;    
})();
console.log("a defined? " + (typeof a !== 'undefined'));    
console.log("b defined? " + (typeof b !== 'undefined'));

Output:

a defined? false
b defined? true

Description: In this code snippet, an Immediately Invoked Function Expression (IIFE) is used. Variable a is declared inside the function's scope while variable b is not declared and therefore becomes part of the global scope. When trying to access these variables outside the function, a is undefined but b is defined.

Second Code:

var myObject = { 
   foo: "bar",    
   func: function() {    
       var self = this;    
       console.log("outer func:  this.foo = " + this.foo);    
       console.log("outer func:  self.foo = " + self.foo);    
       (function() {    
           console.log("inner func:  this.foo = " + this.foo);   
           console.log("inner func:  self.foo = " + this.foo); 
       }());    
   }    
};    
myObject.func();

Output:

outer func:  this.foo = bar
outer func:  self.foo = bar
inner func:  this.foo = undefined
inner func:  self.foo = bar

Description:

The important concept here is the usage of this reference inside a function. When it refers to an object's property within that object's method, it simply refers to the object itself. The first two logs show the expected result. However, when an IIFE is used, this now refers to the global object (Window object), hence resulting in undefined. On the other hand, using self within the inner function retains the value of foo from the object, providing the expected output.

Answer 5

Answer №3

This code snippet showcases an immediately invoking function. The variables a and b are scoped inside the function, while console.log is outside of it. As a result, they will be undefined.

console.log("a defined? " + (typeof a !== 'undefined')); //output a defined false
console.log("b defined? " + (typeof b !== 'undefined')); //output b defined true

(function() {
  var a = b = 3;
})();
console.log("a defined? " + (typeof a !== 'undefined'));
console.log("b defined? " + (typeof b !== 'undefined'));

I have provided comments within the following code snippet for clarity:

var myObject = {
  foo: "bar",
  func: function() {
    // here 'this' and 'self' will refer to the myObject
    var self = this;
    console.log("outer func:  this.foo = " + this.foo); //outer func:  this.foo = bar    
    console.log("outer func:  self.foo = " + self.foo); //outer func:  self.foo = bar    
    (function() {
      // here 'self' will refer to the myObject context where as 
      // 'this' will refer to the window object.
      // Since foo is not defined in the window object, it will output undefined
      console.log("inner func:  this.foo = " + this.foo); //inner func:  this.foo = undefined  
      console.log("inner func:  self.foo = " + self.foo); //inner func:  self.foo = bar
    }());
  }
};
myObject.func();

Answer 6

This code snippet showcases an immediately invoking function. The variables a and b are scoped inside the function, while console.log is outside of it. As a result, they will be undefined.

console.log("a defined? " + (typeof a !== 'undefined')); //output a defined false
console.log("b defined? " + (typeof b !== 'undefined')); //output b defined true

(function() {
  var a = b = 3;
})();
console.log("a defined? " + (typeof a !== 'undefined'));
console.log("b defined? " + (typeof b !== 'undefined'));

I have provided comments within the following code snippet for clarity:

var myObject = {
  foo: "bar",
  func: function() {
    // here 'this' and 'self' will refer to the myObject
    var self = this;
    console.log("outer func:  this.foo = " + this.foo); //outer func:  this.foo = bar    
    console.log("outer func:  self.foo = " + self.foo); //outer func:  self.foo = bar    
    (function() {
      // here 'self' will refer to the myObject context where as 
      // 'this' will refer to the window object.
      // Since foo is not defined in the window object, it will output undefined
      console.log("inner func:  this.foo = " + this.foo); //inner func:  this.foo = undefined  
      console.log("inner func:  self.foo = " + self.foo); //inner func:  self.foo = bar
    }());
  }
};
myObject.func();

Answer 7

Answer №4

let newObj = { 
    name: "John",    
    greet: function() {    
        let self = this;    
        console.log("Hello, my name is " + this.name);       
        (function() {    
            console.log("This is an inner function: " + this.name);   
            console.log("This is an inner function using 'self': " + self.name); 
        }());    
    }    
};    
newObj.greet();

Answer 8

let newObj = { 
    name: "John",    
    greet: function() {    
        let self = this;    
        console.log("Hello, my name is " + this.name);       
        (function() {    
            console.log("This is an inner function: " + this.name);   
            console.log("This is an inner function using 'self': " + self.name); 
        }());    
    }    
};    
newObj.greet();

Seeking assistance with producing results

Answer №1

Answer №2

Answer №3

Answer №4

Similar questions

What could be the reason behind the success of my API call in Chrome while encountering failure when implemented in my

The value of Express session within the callback is not retained when accessed outside

Differences between urlencoded and form-data in Node.js

Retrieve various key-value pairs from the JSON data in the global market API using AJAX

What is the proper way to reference an EJS function that is declared in a different EJS file?

Is it advisable to subscribe to the entire database upon startup in Meteor?

Converting JSON objects into TypeScript classes: A step-by-step guide

The types 'X' and 'string' do not intersect

How to import a page from a different component in the Next.js application router

Issue with React not properly closing the dialog box

Guide on emphasizing a div when the page's validity is not true

Displaying an array value instead of a new value list in a React component

Merging a prop of array type in a Vue component

A different approach to joining strings

Error message: When using the Semantic UI React Modal, the Portal.render() function requires a valid React element to be returned, otherwise

What is the best way to guide users to different pages on the website without disrupting the socket connection?

Updating token (JWT) using interceptor in Angular 6

Error in Typescript: The property 'children' is not included in the type but is necessary in the 'CommonProps' type definition

Add an input element to a form fieldset by employing vue

There is no result being returned by Model.findOne()