Salesforce JS-Dev-101 Exam Questions

Comprehensive and Detailed

Assuming SaleItem inherits from Item via prototype (e.g. SaleItem.prototype = Object.create(Item.prototype)):

Lines 01--02: create regItem and saleItem.

Line 03: define Item.prototype.description.

Now both regItem and saleItem (via inheritance) have a description method from Item.prototype.

Line 04: regItem.description() 'This is a Scarf'.

Line 05: saleItem.description() 'This is a Shirt' (same method, but this.name is 'Shirt').

Line 07: SaleItem.prototype.description = ... overrides description only for SaleItem instances going forward.

If we imagine calling regItem.description() and saleItem.description() again after line 07:

regItem.description() still uses Item.prototype.description 'This is a Scarf'.

saleItem.description() now uses SaleItem.prototype.description 'This is a discounted Shirt'.

Those four lines correspond to option B.

________________________________________

Comprehensive and Detailed Explanation From JavaScript Knowledge:

We want to convert the number 1982 to a string.

Check each option:

A . numValue.toText()

There is no standard toText() method on numbers.

This will result in TypeError: numValue.toText is not a function.

B . String(numValue);

String() as a function converts its argument to a string.

String(1982) returns '1982'.

This is correct.

C . '' + numValue;

'' is a string; + with a string operand performs string concatenation.

'' + 1982 '1982'.

This is a common shorthand for number-to-string conversion.

D . numValue.toString();

Number.prototype.toString() converts the number to its string representation.

1982..toString() or (1982).toString() returns '1982'.

For the variable, numValue.toString() is valid: '1982'.

E . (String)numValue;

This is not valid JavaScript casting syntax; it is more like a C/Java-style cast.

In JavaScript, that is parsed as a grouping expression (String) and then numValue; it does not convert numValue to a string.

Thus the correct answers are:

B . String(numValue);

C . '' + numValue;

D . numValue.toString();

Relevant concepts: primitive type conversion, String() casting, .toString(), coercion via + with strings.

________________________________________

________________________________________

Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge

JavaScript has one numeric data type for all real numbers, whether integers or decimals.

This type is simply called:

Number

It follows the IEEE 754 double-precision floating-point standard internally,

but JavaScript does not expose separate types like float, double, or decimal.

Therefore:

It is not Float JavaScript does not have float primitives.

It is not Double this refers to the underlying IEEE 754 representation, but JavaScript's type is still just ''Number.''

It is not Decimal JavaScript has no built-in decimal type.

The correct answer is Number.

________________________________________

JavaScript Knowledge Reference (text-only)

JavaScript has a single numeric type: Number.

All numbers---integers, fractions, floating point---use the Number type.

==================================================

A: Yes. You can run arbitrary JS in the console (even if it doesn't touch the page).

B: Yes. You can inspect and modify DOM nodes via JS.

C: Performance reports are mainly in the Performance tab, not the console.

D: Yes. You can alter the DOM and redefine or override JS functions/variables at runtime.

E: You can read and set document.cookie, but HttpOnly ''security cookies'' cannot be read or changed from JS.

________________________________________