Refer to code below: Let productSKU = ‘8675309’ ; A developer has a requirement to generate SKU numbers that are always 19 characters lon, starting…

The goal is to transform '8675309' into 'sku0000000008675309'. This is a two-step process using chained string methods.

1. productSKU.padStart(16, '0'): The original 7-character string is padded with zeros at the start until it reaches a length of 16. This results in '0000000008675309'. The target length is 16 because the final length is 19, and the 'sku' prefix is 3 characters (19 - 3 = 16).

2. .padStart(19, 'sku'): The 16-character result from the first step is then padded at the start with 'sku' until it reaches the final target length of 19, yielding the correct value.

A. The second padStart call is invalid; its first argument must be a target length (a number), not the string 'sku'.

B. padEnd incorrectly adds padding to the right of the number. The second padStart call is also syntactically invalid.

C. padEnd incorrectly adds padding to the right of the number, which does not meet the requirement of placing zeros between the prefix and the SKU.

1. MDN Web Docs (Mozilla): String.prototype.padStart(). The documentation specifies the syntax padStart(targetLength

padString). It states

"The padStart() method pads the current string with another string (multiple times

if needed) until the resulting string reaches the given length." This supports the two-step padding logic in option D.

2. ECMAScript® 2023 Language Specification (ECMA-262

14th edition): Section 22.1.3.18 String.prototype.padStart ( maxLength [

fillString ] ). This official specification defines the abstract operation StringPad

which is invoked by padStart. It confirms that the first argument

maxLength

is coerced to an integer length

and the padding is applied to the start of the string. This validates the method's usage in option D and invalidates the syntax in option A.

3. MDN Web Docs (Mozilla): String.prototype.padEnd(). This document explains that padEnd adds padding to the end (right side) of a string

which is contrary to the requirement of adding a prefix and zero-padding on the left. This confirms why options B and C are incorrect.