The ______ statement is used to specify a new condition to test if the first condition is false.
- else if
- else
- if else
- switch
The else if statement is used to specify a new condition to test if the first condition in an if statement is false. It allows for branching in code execution based on multiple conditions. It's a fundamental control structure in JavaScript.
You're debugging a piece of code that is returning an array in an unexpected order after a sort() method is applied. What could be a likely cause for this behavior given the default behavior of sort()?
- The array has mixed data types
- The sort() function is asynchronous
- The array elements are all numbers
- The array elements are strings
JavaScript's sort() method by default converts elements to strings and then compares their UTF-16 code units. This means that if the array contains mixed data types, the sorting order might be unexpected. For proper sorting, you should provide a compare function as an argument to sort().
A piece of code is unexpectedly returning -Infinity. What arithmetic operation could be causing this?
- Division (/)
- Addition (+)
- Exponentiation (**)
- Multiplication (*)
When a piece of code returns -Infinity, it is usually due to a division operation where you are dividing a finite number by zero. In JavaScript, dividing any finite number by zero results in -Infinity. Make sure to handle cases where division by zero can occur to prevent unexpected -Infinity values in your code.
When the interpreter encounters the following code var x = "5"; the typeof x will be _________.
- "string"
- "number"
- "boolean"
- "undefined"
In JavaScript, the typeof operator is used to determine the data type of a variable. When var x = "5"; is encountered, the value of x is a string because it is enclosed in double quotes. Therefore, typeof x will return "string". It's important to note that JavaScript is dynamically typed, meaning the type of a variable can change during runtime.
How can you add a method to an object in JavaScript?
- a) By using the Object.addMethod() method.
- b) By defining a function and assigning it as a property of the object.
- c) By using the Object.method() function.
- d) By using the object.method = function() syntax.
You can add a method to an object in JavaScript by defining a function and assigning it as a property of the object. For example, myObject.myMethod = function() { /* method code */ };. While you can use various patterns and techniques for method definition, there's no standard Object.addMethod() or Object.method() function.
How does hoisting behave in function declarations in JavaScript?
- Function declarations are moved to the top of their containing scope during compilation.
- Function declarations are not affected by hoisting.
- Hoisting only applies to variables, not functions.
- Function declarations are moved to the bottom of the code.
In JavaScript, hoisting is the mechanism by which variable and function declarations are moved to the top of their containing scope during compilation. This means that you can call a function declared with function before it appears in your code, and it will still work. However, it's important to note that only the declarations are hoisted, not the initializations. Understanding hoisting is crucial for writing clean and maintainable JavaScript code.
A _________ object is used to perform HTTP requests in AJAX.
- XMLHttpRequest
- JSON
- DOM
- Fetch
In AJAX (Asynchronous JavaScript and XML), the XMLHttpRequest object is used to perform HTTP requests asynchronously. It allows you to send and receive data from a server without refreshing the entire web page.
In JavaScript, when a function is defined inside another function, the inner function has access to the ________ of the outer function due to lexical scoping.
- Variables
- Properties
- Methods
- Parameters
In JavaScript, when a function is defined inside another function, the inner function has access to the variables of the outer function due to lexical scoping. Lexical scoping means that the inner function "remembers" the scope in which it was created, allowing it to access and manipulate variables defined in the outer function. This behavior is one of the fundamental aspects of closures in JavaScript.
_________ allows a function to access all the variables, as well as other functions, that are in its scope.
- Closures
- Callbacks
- Promises
- Events
Closures allow a function to access all the variables and other functions that are in its scope when the function was created. This feature enables powerful patterns in JavaScript, like data encapsulation and private variables. Understanding closures is essential for advanced JavaScript development.
Consider a situation where you have a switch statement inside a function, and forgetting to include a break statement leads to a bug. How might this bug manifest in the function’s behavior?
- The function might return the value associated with the first matching case, and all subsequent code within the switch block will execute as well.
- The function will throw an error, indicating a missing "break" statement, and won't execute any code within the switch block.
- The function will automatically insert "break" statements at the end of each case, ensuring correct behavior.
- The function will ignore the switch statement and continue executing the code outside of the switch block.
If you forget to include a "break" statement in a switch case, it will lead to a bug where the function may not behave as expected. Instead of stopping after the first matching case, the switch statement will "fall through" to subsequent cases, causing unintended behavior. The correct option is to use a "break" statement to exit the switch block after handling a case. JavaScript doesn't automatically insert "break" statements, and it doesn't throw an error for missing "break" statements.