Which two syntax examples correctly initialize a value to the variable strLang?
A. let strLang = 'javascript';
B. const strLang = 'java' + 'script';
C. let strLang = javascript;
D. str strLang = 'javascript';
ANSWER
...
Which two syntax examples correctly initialize a value to the variable strLang?
A. let strLang = 'javascript';
B. const strLang = 'java' + 'script';
C. let strLang = javascript;
D. str strLang = 'javascript';
ANSWER:
A. let strLang = 'javascript';
B. const strLang = 'java' + 'script';
Additional Info:
Note that C doesn't have a value that has single quotes around the word 'javascript' and
for D, 'str' is not a proper identifier
Which statement sorts the following number array so it is in ascending order? const arr
= [7, 3, 400, 10];
A. arr.sort();
B. arr.sort((a, b) => a - b);
C. arr.sort((a, b) => a < b);
D. arr.sort((a, b) => b - a);
ANSWER:
B. arr.sort((a, b) => a - b);
Additional Info:
A. The sort() function sorts values as strings, which will sort this as [10, 3, 400, 7].
C. The compare function expects a positive, negative, or 0 to be returned.
D. The compare function will actually reverse the order of the numbers.
Which statement sorts the following string array so it is in descending order? const arr =
["Banana", "Orange", "Apple", "Mango"];
A. arr.sort();
B. arr.sort((a, b) => a - b);
C. arr.reverse();
D. arr.sort((a, b) => b - a);ANSWER:
C. arr.reverse();
Additional Info:
A. The sort() function sorts values as strings in ASCENDING order: ["Apple", "Banana",
"Mango", "Orange"];
B,D. Expect a number array.
What are the different data types used in JavaScript?
ANSWER:
There are 8 basic data types in JavaScript:
1. Number for numbers of any kind: integer or floating-point, integers are limited by
±((2^53)-1).
2. BigInt is for integer numbers of arbitrary length.
3. String for strings. A string may have zero or more characters, there's no separate
single-character type.
4. Boolean for true/false.
5. NULL for unknown values - a standalone type that has a single value null. Note,
typeof null returns "object" even though it is NOT and object.
6. Undefined for unassigned values - a standalone type that has a single value
undefined.
7. Object for more complex data structures.
8. Symbol for unique identifiers.
Which collections of data are ordered by a key?
ANSWER:
Map and set objects.
What is the proper syntax for adding placeholders in template literals?
ANSWER:
Use a dollar sign followed by curly brackets:
${expression}.
Additional Info:
let name = "John";
// embed a variable
alert( `Hello, ${name}!` ); // Hello, John!
// embed an expression
alert( `the result is ${1 + 2}` ); // the result is 3Note this only works if you use backticks, `, and not single(') or double(") quotes
otherwise the results will be shown as literal, ie: Hello, ${name}!
How do you instantiate a value as a BigInt?
A. Nothing, JavaScript will automatically cast a number to a BigInt if the value is greater
than ((2^53) - 1)
B. const bigInt = BigInt.parse(1234567890123456789012345678901234567890);
C. const bigInt = 1234567890123456789012345678901234567890n;
D. const bigInt = BigInt.parse('1234567890123456789012345678901234567890');
ANSWER:
C. const bigInt = 1234567890123456789012345678901234567890n;
Additional Info:
BigInt does NOT work in IE.
Given the following Animal constructor:
function Animal(size, age) {
this.size = size;
this.age = age;
this.canTalk = false;
}
Which method creates a new instance of the object?
A. Object.create('Animal');
B. new Animal('large', 10);
C. Object.prototype(Animal);
D. Object.new(Animal);
ANSWER:
B. new Animal('large', 10);
Additional Info:
A. The create method needs the object name without quotes.
C. This is an incorrect way to use a prototype. Prototypes are used to add methods to
existing constructors.
D. This is not the correct way to use the new keyword. It is not a method.
A developer wants to use a module called DatePrettyPrint. This module exports one
default function called printDate().
How can a developer import and use the printDate() function?
A. import printDate() from '/path/DatePrettyPrint.js';
printDate();
B. import printDate from '/path/DatePrettyPrint.js';
printDate();
C. import DatePrettyPrint from '/path/DatePrettyPrint.js';
DatePrettyPrint.printDate();
D. import printDate from '/path/DatePrettyPrint.js';
DatePrettyPrint.printDate();
ANSWER:
B. import printDate from '/path/DatePrettyPrint.js';printDate();
Additional Info:
Once imported by name, you must call the imported method directly by name.
You must call the methods directly or use the * to import all methods.
When using the `const` identifier to create an instance of an object, are the properties
changeable?
ANSWER:
Yes.
An object declared as `const` can be modified. The `const` fix
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