Salesforce JavaScript Developer Practice Exam

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• What is the output of the following code snippet when logged to the console? const settings = { username: 'lydiahallie', level: 19, health: 90 }; const data = JSON.stringify(settings, ['level', 'health']); console.log(data);
• When you execute the code const numbers = [1, 2, 3]; numbers[10] = 11; console.log(numbers); what will be the output?
• In the provided code, what is the value of event.target when the button is clicked in the nested structure of divs?
• Given two promises, which of the following correctly executes them in sequence?
• What is the outcome of attempting to change the dept property of returnTarget after calling Object.freeze(returnTarget)?
• How long does sessionStorage data persist?
• What are the three phases of event propagation in JavaScript?
• What is the inline command a developer can use in an editor to set a breakpoint?
• What will the console log output when modifying the greeting property?
• What does the spread operator return when applied to a string, e.g., [...'Lydia']?
• In the context of promises, what does the term "pending" mean?
• What is the result of filtering the array [1, 4, 9, 16] for odd numbers?
• What will be the output from the loop that continues when i equals 3?
• What happens when a developer executes npm install with incompatible peer dependencies?
• If test assertions for a method still pass after the method is updated, what should be done?
• Given the expression +true; !'Lydia'; what will be the outputs?
• What will the output be when message.showMessage() is called in the context of: let message = { hello: 'Hello', names: ['Sue', 'Joe'], showMessage: function() { this.names.forEach(function(name) { console.log(this.hello + ' ' + name); }); } }?
• What is the result of using regex /[A-Z]/ with the g flag on the phrase 'The quick brown fox jumps over the lazy dog. It barked.'?
• What results will be output when comparing primitive and object types using == and ===?
• What will be the output of the following code: const person = { name: 'Lydia' }; function sayHi(age) { return `${this.name} is ${age}`; } console.log(sayHi.call(person, 21)); console.log(sayHi.bind(person, 21));?
• In which scenario will the console.assert method provide output?
• What does the eval function return when a String object is evaluated?
• What will be the log output for the following code? const json = '{"result":true, "count":42}'; const obj = JSON.parse(json); console.log(obj.result);
• What will happen when referencing a non-existent property of an object in JavaScript?
• What will be logged when executing the function getPersonInfo with tagged template literals?
• What will be the output of the following code: console.log(x); var x = 10;
• How can the assertion be corrected if the sum3 method is updated to multiply numbers?
• What is the result of using an undeclared variable in non-strict mode?
• What is the output of the given code that uses 'use strict'?
• Which keyword is used to refer to the parent class within a derived class method?
• What is the correct code to replace the last line with an async/await function for retrieving a book?
• What does the popstate event signify in the context of history manipulation?
• What will be logged when the following code is executed? [1, 2, 3, 4].reduce((x, y) => console.log(x, y));
• Which type of loop should be used to iterate over elements directly in an array?
• What is the output of the following console log for an object with duplicate keys?
• What does the Promise.race method return when multiple promises are passed to it?
• Which of the following is not an attribute of Object.defineProperty()?
• What does the method element in logArrayElements function display as the output?
• What will be the console order of output for the provided asynchronous code snippet?
• What will be the output after using splice to add 'Feb' in the array ['Jan', 'March', 'April', 'June']?
• What is the output of the function sayHi when executed as follows: function sayHi() { return (() => 0)(); } console.log(typeof sayHi());?
• What is one of the main benefits of using popular frameworks in development?
• What will the output be when checking for property existence with hasOwnProperty?
• When using await, what must you ensure about the function it's used in?
• Which statement describes the function of Object.freeze() on an object?
• What will the output be for this code? const numbers = [1, 2, 3]; numbers.push(4); console.log(numbers);
• What will be the result of the following code: arr.map(x => x * 2) on the array [1, 4, 9, 16]?
• What will be the output logs of the following code snippet involving two person objects?
• What will console.log(number++) and console.log(++number) output for the variable defined as let number = 0?
• What will be the output of console.log(x); let x = 10;?
• What will Object.keys(emp) return if emp = {name: "Santanu", dept: "IT"}?
• What is the primary reason a variable defined inside a function cannot be accessed outside of that function?
• What will be the output of the code snippet that uses var within a setTimeout?
• What will the output be when using eval on the valueOf method of a String object containing '2 + 2'?
• What will the output of the following code be: class Animal { constructor(name) { this.name = name; } printName() { console.log(this.name); } } console.log(typeof Animal);?
• What will be the output when executing this code? let x = 10; const test = (y = (x += 10)) => y; console.log(test());
• Which method can be used to prevent new properties from being added to an object?
• What is the difference between var, let, and const in terms of scope?
• Which of the following is NOT a Promise state?
• In which scenario will an arrow function not bind its own `this`?
• What are the two main categories into which everything in JavaScript can be classified?
• If a paragraph is clicked in a nested div structure, what will be the order of logged outputs?
• Given the code: const myDt = new Date(); console.log(myDt + 10); what will be the output?
• Do all objects in JavaScript have prototypes?
• Which event should a developer use to detect changes in browser history when using the History API?
• How is the age property accessed if it was set on the instance rather than the prototype?
• Which statement about the bird and mouse objects is correct?
• Which of the following values are considered falsy in JavaScript?
• What is the output of the generator function below after two calls? function* generator(i) { yield i; yield i * 2; } const gen = generator(10); console.log(gen.next().value); console.log(gen.next().value);
• Which of the following correctly defines a function that adds two numbers?
• What will be the output when calling the added prototype method for Strings?
• What will be the console output when redefining a variable with var?
• Which constructor is correct for successfully extending the Dog class? class Dog { constructor(name) { this.name = name; } }; class Labrador extends Dog { // ... }
• What will happen if you attempt to use let for re-declaring a variable within the same scope?
• What is the output of the following code snippet when logged to the console? let num = 10; const increaseNumber = () => num++; const increasePassedNumber = number => number++; const num1 = increaseNumber(); const num2 = increasePassedNumber(num1); console.log(num1); console.log(num2);
• What will happen if you call checkAge with an object having age as 18?
• What does JSON.stringify do?
• What is the difference between a function's prototype and an object's prototype?
• What will the console output be when searching for uppercase letters in a given paragraph?
• What is a primary benefit of using breakpoints in JavaScript debugging?
• Which of the following is true regarding primitive value comparison in JavaScript?
• What will happen if you attempt to call getFullName on a member instance of the Person constructor?
• What will console.log(lydia) and console.log(sarah) output when using the Person constructor correctly and incorrectly?
• What will be the output of the following code: greetign = {};?
• What will the output be after running this code: (() => { let x, y; try { throw new Error(); } catch (x) { (x = 1), (y = 2); console.log(x); } console.log(x); console.log(y); })();?
• What happens to the name property after calling Object.seal(emp) and then delete emp.name?
• What happens when you add properties to a function in JavaScript?
• What is an effect of using Object.assign() in JavaScript?
• What is the log output for the following code: console.log(JSON.stringify([new Number(3), new String('false'), new Boolean(false)]));
• What will be logged when executing the following code? let person = { name: 'Lydia' }; const members = [person]; person = null; console.log(members);
• What does the unary plus operator do in JavaScript?
• Which of the following is NOT a basic DOM data type?
• What will be the output when the following code is executed: const foo = () => console.log('First'); const bar = () => setTimeout(() => console.log('Second')); const baz = () => console.log('Third'); bar(); foo(); baz();?
• What will be the output when executing: console.log(typeof typeof 1);?
• What is the output of the following code? [[0, 1], [2, 3]].reduce( (acc, cur) => { return acc.concat(cur); }, [1, 2]);
• What is the value of the variable sum defined with eval?
• When is an async function typically resolved?
• What is the output of the expression !!null;
• What will be the output of the following code: const arr = [1, 2, 3]; arr.push(6); console.log(arr); arr.pop(); console.log(arr); arr.shift(); console.log(arr); arr.unshift(8); console.log(arr);?
• What will the output be when message.showMessage() is executed for the following arrow function context: let message = { hello: 'Hello', names: ['Sue', 'Joe'], showMessage: function() { this.names.forEach(name => { console.log(this.hello + ' ' + name); }); } }?
• What is the output of the for-in loop iterating over the object person? const person = { name: 'Lydia', age: 21 }; for (const item in person) { console.log(item); }
• What will be logged to the console when showContact is executed with the parameters: showContact('Sue', 'Johnson', 'Developer', 'Architect');?
• What are the most crucial items in your npm package.json file for publishing a package?