Pure Functions & Immutability

Preview — 3 of 10 questions

What best describes first-class functions in JavaScript?

javascript

const add = function(a, b) {
  return a + b;
};

AFunctions can only be used inside classes.

BFunctions can be passed as arguments, returned from other functions, and assigned to variables.

CFunctions can only be used in the global scope.

DFunctions can only return numbers.

Which of the following is an example of a higher-order function?

javascript

function map(array, callback) {
  const result = [];
  for (let i = 0; i < array.length; i++) {
    result.push(callback(array[i]));
  }
  return result;
}

map([1, 2, 3], function(x) {
  return x * 2;
}); // [2, 4, 6]

AA function that returns a number.

BA function that takes another function as an argument or returns a function.

CA function that does not return anything.

DA function that performs simple arithmetic operations.

What will the following code output?

javascript

function add(x, y) {
  return x + y;
}

function calculate(fn, a, b) {
  return fn(a, b);
}

console.log(calculate(add, 2, 3));

Cundefined

DError

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