How can you add a new property to a JavaScript object
- a) By using the Object.assign() method.
- b) By using the Object.addProperty() method.
- c) By simply assigning a value to a new property name.
- d) By using the addProperty() function.
You can add a new property to a JavaScript object by simply assigning a value to a new property name. For example, myObject.newProperty = 'some value';. While you can use methods like Object.assign() to copy properties from one object to another, it's not used for adding new properties. There's no Object.addProperty() or addProperty() method.
A _______ is a self-contained block of code that manipulates data, and can be thought of as an object in object-oriented programming.
- Function
- Module
- Class
- Closure
A Module is a self-contained block of code in JavaScript that manipulates data and can be thought of as an object in object-oriented programming. Modules help encapsulate functionality and data, providing a clean and organized code structure.
In JavaScript, the _________ property is a reference to an object from which the current object inherits properties.
- prototype
- this
- parent
- child
In JavaScript, the prototype property is a reference to an object from which the current object inherits properties and methods. When you access a property or method on an object, JavaScript first looks for it on the object itself and then, if not found, on its prototype. Understanding prototypal inheritance is crucial in JavaScript.
The _______ method returns the removed item when an element is removed from an array.
- shift()
- pop()
- remove()
- splice()
The pop() method in JavaScript removes the last element from an array and returns that removed element. It's useful when you need to remove and capture the last item in an array. For instance, let removed = myArray.pop() would remove the last element from myArray and store it in the removed variable.
The concept of closures and lexical scoping in JavaScript is based on the ________ principle.
- Scope
- Encapsulation
- Abstraction
- Inheritance
The concept of closures and lexical scoping in JavaScript is based on the "Scope" principle. In JavaScript, scope determines the accessibility of variables and functions in different parts of your code, and closures are a powerful feature that leverages lexical scope to maintain access to variables even after their containing functions have finished executing.
How does the "this" keyword behave in arrow functions inside methods?
- It refers to the instance of the class containing the method.
- It refers to the global object (e.g., window in the browser).
- It throws an error since arrow functions cannot be used inside methods.
- It refers to the parent function's "this" value.
In arrow functions inside methods, the "this" keyword retains the value of the outer scope, typically the class instance. This behavior is different from regular functions, which have their own "this" binding. Understanding this behavior is crucial in object-oriented JavaScript programming.
The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to _______ it to a single value.
- multiply
- concatenate
- reduce
- filter
The reduce() method in JavaScript is used to apply a function to an accumulator and each element of the array (from left to right) to reduce it to a single value. It's often used for tasks like summing up values or aggregating data. The correct option is reduce.
To declare a string variable named text with the value 'Hello World' in JavaScript, you would write _________.
- var text = "Hello World";
- var text := "Hello World";
- string text = "Hello World";
- text = "Hello World";
To declare a string variable in JavaScript, you use the var keyword followed by the variable name (text) and assign the value (Hello World) using the equal sign (=). The correct syntax is var text = "Hello World";. Variables are case-sensitive in JavaScript, so make sure the variable name matches the case.
When would you want to use Object.create(null) instead of {} to create a new object?
- When you need an object with no prototype chain to avoid inheriting properties or methods unintentionally.
- When you want an object that can't be modified or extended further.
- When you need an object with a predefined set of properties and methods for a specific use case.
- When you want to create an empty object with the default prototype chain.
Object.create(null) is used when you need an object with no prototype chain (a "null prototype"), which means it won't inherit any properties or methods from Object.prototype. This can be useful for creating objects where you want complete control over the properties and avoid unintentional inheritance.
What is the purpose of the innerHTML property in JavaScript?
- To access the element's content
- To set the element's ID
- To toggle element visibility
- To retrieve the element's tag name
The innerHTML property in JavaScript is used to access the content of an HTML element. It allows you to retrieve or modify the HTML content within the element, including any child elements, text, or HTML tags.