Which statement is true regarding function scope in JavaScript?
- Functions can access variables from outer scopes.
- Variables declared inside functions have global scope.
- Variables declared inside functions have function scope.
- Variables declared inside functions are accessible only within that function's block.
In JavaScript, variables declared inside functions have function scope, meaning they are only accessible within that function. This is important for encapsulation and avoiding variable conflicts. Variables declared outside of functions have global scope, and functions can access variables from outer scopes, but the reverse is not true.
Imagine you are implementing a feature to upload a file to the server. Which HTTP method would be most appropriate to use with the Fetch API for this purpose?
- GET
- POST
- PUT
- DELETE
To upload a file to the server, you would use the POST HTTP method with the Fetch API. The POST method is used for submitting data to be processed to a specified resource, which is suitable for file uploads. GET, PUT, and DELETE have different purposes.
How to declare a constant array in JavaScript?
- const arr = [];
- const arr = new Array();
- const arr = {}
- const arr = [1, 2, 3];
To declare a constant array in JavaScript, you can use the const keyword followed by square brackets, like const arr = [];. The const keyword ensures that the variable arr cannot be reassigned, making it a constant array.
You are debugging a web page and find that an element isn't being selected as expected with document.querySelector('.example'). What could be a possible reason if the class name is correct?
- Element not present in the DOM
- Element is inside an iframe
- JavaScript not loaded before the query
- Class name contains special characters or spaces
If an element with the correct class name isn't being selected with document.querySelector('.example'), a possible reason could be that the element is not present in the DOM at the time of the query. Ensure that the element you are trying to select exists and is rendered when your JavaScript runs. The other options are less likely causes.
In JavaScript, the _______ method is used to create a new object using an existing object as the prototype of the newly created object.
- Object.create()
- Object.assign()
- Object.extend()
- Object.instantiate()
In JavaScript, the Object.create() method is used to create a new object with the specified prototype object. It allows you to create objects that inherit properties and methods from an existing object, making it a powerful tool for prototypal inheritance.
The switch statement evaluates expressions based on their _________.
- Values
- Cases
- Conditions
- Labels
The switch statement in JavaScript evaluates expressions based on their cases. Each case represents a possible value that the expression can take, and the code block associated with the matching case is executed. This allows for multiple execution paths based on different values of the expression.
When using a for...of loop with strings, each iteration will provide a single _______.
- Character
- Word
- Line
- Number
When using a for...of loop with strings, each iteration will provide a single character. This loop is useful for breaking down strings into individual characters for various processing tasks, such as counting characters or manipulating them individually.
In which context does the "this" keyword not refer to the object that calls the function?
- Global context
- Method context
- Function context
- Constructor context
The "this" keyword in JavaScript does not refer to the object that calls the function in the global context. In the global context, "this" points to the global object, which is usually the "window" object in browsers. This can be a source of confusion, so it's essential to understand the various contexts in which "this" behaves differently.
You're developing a Node.js application and notice that the "this" keyword inside a regular function, defined in the global scope, refers to something different than you're used to in client-side JavaScript. What does "this" refer to in this context?
- It refers to the Node.js global object (e.g., "global" or "window")
- It refers to the "exports" object
- It refers to the "module.exports" object
- It refers to the function itself
In Node.js, when you define a regular function in the global scope (outside any function or module), "this" inside that function refers to the Node.js global object (e.g., "global" in Node.js or "window" in the browser). This behavior is different from client-side JavaScript, where "this" in the global scope refers to the global window object.
What is a closure in JavaScript?
- A secure way to store passwords
- A private function
- A way to handle exceptions
- A function that remembers its lexical scope
A closure in JavaScript is a function that "remembers" its lexical scope, even when it's executed outside that scope. This allows the function to maintain access to variables from its parent scope, creating a powerful mechanism for encapsulation and data privacy.