JavaScript Syntax Mocktest

All of the options (A, B, and can be used to convert a string to a number in JavaScript: - parseInt("10") converts a string to an integer. - parseFloat("10.5") converts a string to a floating-point number. - Number("10") converts a string to a number. Therefore, option D, "All of the above," is correct for converting a string to a number in JavaScript.

Option A correctly declares a JavaScript object named 'person' with properties 'name' and 'age' using curly braces {} and key-value pairs. Option B uses parentheses () and '=>' arrows, which are not valid for object declaration. Option C uses square brackets [], which are used for arrays, not objects. Option D uses 'var' instead of 'let' or 'const' and correctly declares an object.

The 'push' method in JavaScript is used to add a new element to the end of an array. Therefore, option A, 'colors.push('blue');', is correct for adding a new element ('blue') to the end of the array 'colors'. Option B, 'colors.add('blue');', is incorrect as there is no 'add' method for arrays in JavaScript. Options C and D are also incorrect ways of adding elements to an array.

The 'break' statement in a JavaScript switch case is used to exit the switch statement once a matching case is found and executed. Without the 'break' statement, execution would continue to the next case, leading to unexpected behavior. Therefore, option B, 'To exit the switch statement', is correct for explaining the purpose of the 'break' statement in a JavaScript switch case.

Option A correctly declares a JavaScript class named 'Rectangle' using the 'class' keyword followed by curly braces {}. This is the modern ES6 syntax for declaring classes in JavaScript. Options B, C, and D are incorrect ways of declaring a class. Option B is an object declaration, option C is a constructor function, and option D is invalid syntax for a class declaration.

To access the last element of a JavaScript array, you can use the expression 'colors[colors.length - 1];'. The 'length' property of an array returns the number of elements in the array, so 'colors.length - 1' gives the index of the last element. Therefore, option A is correct for accessing the last element of the array 'colors'.

Option A correctly declares a JavaScript arrow function named 'add' that takes two parameters 'a' and 'b' and returns their sum using the arrow function syntax. Arrow functions provide a concise way to write functions, especially for simple one-liners like this. Options B, C, and D use different syntaxes for function declaration but are not arrow functions. Therefore, option A is the correct way to declare an arrow function in JavaScript.

The 'continue' statement in a JavaScript loop is used to skip the current iteration and continue to the next iteration of the loop. It allows you to skip certain iterations based on a condition without exiting the loop entirely. Therefore, option B, 'To skip the current iteration', is correct for explaining the purpose of the 'continue' statement in a JavaScript loop.

The 'pop' method in JavaScript is used to remove the last element from an array and return that element. Therefore, option A, 'colors.pop();', is correct for removing the last element from the array 'colors'. Options B, C, and D do not represent valid methods for removing the last element of an array in JavaScript.

Wrapping a JavaScript function in parentheses () is a common way to prevent it from executing immediately. This technique is often used for self-invoking functions (IIFE) or when defining functions dynamically. Options A, B, and D are unrelated to preventing immediate execution of a function. Therefore, option C is correct for preventing a JavaScript function from executing immediately.