FPSC- Programmer (BS-17) - PMD High Yield - 2026 — Test 12

Correct Answer: C. true and false
Explanation: Loose equality treats null and undefined as equal to each other only. Strict equality also compares types. ALSO KNOW (related points): • What does [] + {} evaluate to in JavaScript? → "[object Object]" • What does "b" + "a" + +"a" + "a" evaluate to? → "baNaNa"

Correct Answer: B. [1, 10, 2]
Explanation: With no comparator, sort compares elements as strings. Use .sort((a, b) => a - b) for numbers. ALSO KNOW (related points): • With let arr = [1, 2, 3]; arr[10] = 5;, what is arr.length? → 11 • What does document.querySelectorAll('.temp') return? → A static NodeList of all the matching elements

Correct Answer: C. undefined
Explanation: var declarations are hoisted and initialized to undefined. With let or const, accessing x first throws a ReferenceError (the temporal dead zone). ALSO KNOW (related points): • In which phase do event listeners run by default with addEventListener? → The bubbling phase • What is 'event delegation'? → Attaching one listener to a parent element and handling events from its children through bubbling, using event.target

Correct Answer: B. 3 3 3
Explanation: var is function-scoped, so all the callbacks share one i, which is 3 by the time they run. let would give 0 1 2. ALSO KNOW (related points): • What does localStorage.setItem('n', 5); typeof localStorage.getItem('n') give? → "string"

Correct Answer: A. A D C B
Explanation: Synchronous code runs first, then microtasks (promise callbacks), then macrotasks (setTimeout). ALSO KNOW (related points): • What is a closure in JavaScript? → A function bundled with references to the variables of the scope where it was created, even after that scope has finished • Which statement about Node.js is correct? → It is a JavaScript runtime built on V8 that uses an event-driven, non-blocking I/O model, mainly for server-side code

Correct Answer: C. 5
Explanation: The number is first converted to the string "5e-7", and parseInt then stops at the 'e'. ALSO KNOW (related points): • What does Math.max() (called with no arguments) return? → -Infinity • What does Array.prototype.map() return? → A new array with the callback's result for each element; the original array is unchanged

Correct Answer: D. undefined (in a browser module or script, this is not obj)
Explanation: Arrow functions take their this from the enclosing scope. Use a regular method, show() { ... }, to get obj. ALSO KNOW (related points): • With const obj = {a: 1};, what happens with obj.a = 2;? → It works; const prevents reassigning the variable, not mutating the object • Which string is valid JSON? → {"name": "Karachi", "temp": 35} • What does the spread copy const b = [...a]; do when a contains objects? → It makes a shallow copy: a new array, but the same object references inside it

Correct Answer: A. The promise resolves normally, with response.ok set to false; fetch rejects only on network failure
Explanation: Always check response.ok or response.status. ALSO KNOW (related points): • What does async/await do? → It lets asynchronous promise-based code be written in a synchronous style; await pauses the async function, not the whole thread

Correct Answer: B. innerHTML parses its value as HTML (an XSS risk with untrusted data); textContent treats it as plain text
Explanation: Use textContent for user-supplied data. ALSO KNOW (related points): • What is the difference between event.preventDefault() and event.stopPropagation()? → preventDefault stops the browser's default action (such as following a link); stopPropagation stops the event bubbling to ancestor elements • What is the difference between the DOMContentLoaded and load events? → DOMContentLoaded fires when the HTML is parsed; load waits for all resources, such as images and stylesheets • What is TypeScript? → A typed superset of JavaScript that compiles (transpiles) to plain JavaScript • What is the reliable way to test whether a value x is NaN? → Number.isNaN(x)

Correct Answer: C. Parameterized queries (prepared statements)
Explanation: Escaping input by hand is error-prone. HTTPS does not affect SQL injection at all. ALSO KNOW (related points): • Which HTTP header helps prevent clickjacking? → X-Frame-Options (or CSP frame-ancestors)