Quiz-01

03-09-17

Time Limit: 20min

Q1:

function() {
	var a = 10
	if (a > 5) {
		a = 7
	}
	alert(a)
}

When executed, what value will be alerted to the screen? Why?

1. 7
2. 10
3. null
4. undefined

Answer: 1.

First the variable a is initialized with value 10. Then the code checks if (a > 5), which is true. Therefore, it assigns a the value 7. This later gets alearted on screen.

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Q2:

function() {
	if(true) {
		var a = 5
	}
	alert(a)
}

When executed, what value will be alerted to the screen? Explain.

1. 0
2. 5
3. null
4. undefined

Hint: Javascript has "Function Scope," as opposed to "Block Scope."

Answer: 2. One may think that var a cannot be accessed outside of the scope of if(clause){ scope } and the output should be undefined. However, the scope of a variable is extended to the function(), unlike many other languages, that won't allow you to access a outside of if statement. If that was the case with JavaSript, the output would have been undefined

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Q3:

var a = 5
function first() {
	a = 6
}

function second() {
	alert(a)
}

Assuming I call these functions in order, what value gets alerted and why?

1. 0
2. 5
3. 6
4. null
5. undefined

Answer: 3. var a is a global variable. The first() function runs first and modifies the global value of a to 6. When the second() function runs after that, the new updated value 6 gets alearted.

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Q4: What is the correct syntax for referring to an external script called "xxx.js"? (1 point)

1. <script name="xxx.js">
2. <script src="xxx.js">
3. <script href="xxx.js">

Answer: 2. Following is the correct syntax. Refer to documentation here

<!-- HTML4 and (x)HTML -->
<script type="text/javascript" src="javascript.js"></script>

<!-- HTML5 -->
<script src="javascript.js"></script>

---

Q5:

function whatDoesItDo(val){
	return val ? 1 : 2
}

1. It returns val
2. It always returns 2
3. It returns 1 if val is truthful, otherwise 2

Answer: 3. condition ? expr1 : expr2 is also known as Conditional (ternary) Operator. It can be unpacked into following code:

function whatDoesItDo(val){
	if(val){
		return 1
	}else{
		return 2
	}
}

console.log(whatDoesItDo('test')) // Output: 1
console.log(whatDoesItDo())	// Output: 2

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Q6:

function whatDoesItDo(num){
 return Math.max(0, Math.min(10, num))
}

1. Checks whether the number is between 0 and 10
2. Fits the number passed as a parameter in an interval from 0 to 10
3. Always returns 0

Answer: 2.

• Step:1 First, it takes in the value of num and evaluates the innermost function Math.min(10,num). It finds out the smallest of the two values 10 and num. Let's call it X for now
• Step:2 Now, it evaluates Math.max(0, X). This returns the larger of the two values 0 and X
• In short, step:1 caps the output to less than 10, then step:2 caps the output to above 0

function whatDoesItDo(num){
 return Math.max(0, Math.min(10, num))
}

console.log(whatDoesItDo(5))	// Output: 5
console.log(whatDoesItDo(20))	// Output Max Range: 10
console.log(whatDoesItDo(-20))	// Output Min Range: 0

This function can be unpacked into following:

function whatDoesItDo(num){
	var a = Math.min(10, num)
	b = Math.max(0,a)
	return b
}

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Q7:

function whatDoesItDo(){
	var values = []
	myBlock: {
		values.push('1')
		values.push('2')
		break myBlock
		values.push('3')
	}
	values.push('4')
	return values.join(',')
}

1. It will return the string ‘1,2,3,4’
2. This is not valid JavaScript – it will throw an error
3. It will return the string ‘1,2,4’

Answer: 3.

• First, the code creates an empty array var values = [] called 'values'. Next, it appends/pushes '1' to the array. values = ['1']
• Then '2' is pushed to the array. values = ['1','2']
• Now break myBlock prevents the execution of any following statements after itself, inside myBlock:{ }. So, values.push('3') never gets executed.
• Lastly, values.push('4'), pushed '4' to the array. values = ['1','2','4']
• values.join(',') returns a single string by concatenating all the values in the array values[], seperated by the , symbol
• So the output is 1,2,4

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Q8: What does CSS stand for?

1. Colorful Style Symbols
2. Cascading Style Sheets
3. Computer State Secrets

Answer: 2.

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Q9:

var c = multiply(3,4)
console.log(c)

function multiply(a, b){
	a * b
}

The code above prints undefined in console. Why?

1. Trick question. It does print 12
2. Write your own solution on the right side

Answer: 2. The function does not return any value upon execution. Hence, when var c = multiply(3,4) gets executed, multiply(3,4) does not return 12 as expected, and no value gets assigned to var c. Correct solution is:

var c = multiply(3,4)
console.log(c)

function multiply(a, b){
	return	a * b 	// Return a times b 
}

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Q10: What are the identifiers called that cannot be used as variables or function names?

1. Reserved Words
2. Constants
3. Concrete Terms
4. Favorites

Answer: 1. Here is a list of reserved keywords in ECMAScript 2015

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Q11: What is a block of code called that is used to perform a specific task?

1. Variable
2. Declaration
3. String
4. Function

Answer: 4. "A function is a code snippet that can be called by other code or by itself, or a variable that refers to the function. When a function is called, arguments are passed to the function as input, and the function can optionally return an output. A function in JavaScript is also an object." Reference

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Q12: What is the element called that forms a search pattern out of a sequence of characters?

1. RegExp or Regular Expression
2. Boolean Variable
3. Conditional Argument
4. Event

Answer: 1. "Regular expressions are patterns used to match character combinations in strings. In JavaScript, regular expressions are also objects." Reference

Q13: Write a script that prints a multiple of 5 every 200ms, up to 50.

Answer:

var multiple = 0 // Start with initial value = 0.

var printMultiple = setInterval(function() {
	multiple += 5		// Add 5 to the current multiple value
	console.log(multiple)	// Print the multiple
	
	if (multiple === 50){						// When multiple is 50 
		clearInterval(printMultiple)	// Stop the printMultiple Interval
	}

}, 200)	// 200 ms interval 

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Q14: What is the difference between GET & POST Request

Answer: You may feel that GET requests data from server and POST sends data to server. That would be incorrect. Both are HTTP requests that a client makes to the Server.

The web is based on a very basic client/server architecture that can be summarized as follows: a client (usually a Web browser) sends a request to a server (most of the time a web server like Apache, Nginx, IIS, Tomcat, etc.), using the HTTP protocol. The server answers the request using the same protocol.

GET METHOD

The GET method is the method used by the browser to ask the server to send back a given resource: "Hey server, I want to get this resource." In this case, the browser sends an empty body. Because the body is empty, if a form is sent using this method the data sent to the server is appended to the URL.

POST METHOD The POST method is a little different. It's the method the browser uses to talk to the server when asking for a response that takes into account the data provided in the body of the HTTP request: "Hey server, take a look at this data and send me back an appropriate result." If a form is sent using this method, the data is appended to the body of the HTTP request.

Must Read This Reference : Sending and Receiving Form Data

Q15: Console Log:

module.js:442
		throw err;
		^

Error: Cannot find module 'gulp-sass'
		at Function.Module._resolveFilename (module.js:440:15)
		at Function.Module._load (module.js:388:25)
		at Module.require (module.js:468:17)
		at require (internal/module.js:20:19)
		at Object.<anonymous> (D:\WIP\gulpfile.js:4:12)
		at Module._compile (module.js:541:32)
		at Object.Module._extensions..js (module.js:550:10)
		at Module.load (module.js:458:32)
		at tryModuleLoad (module.js:417:12)
		at Function.Module._load (module.js:409:3)

Why is the error being generated in console. How can you fix it?

Answer: The error is being thrown because the gulp-sass module that is required to execute the script is missing. You need to ensure that the module is within node_modules folder. If not, run npm install gulp-sass --save