String API: String.raw

String.raw provides the string without escaped characters being processed

GIVEN using String.raw as a tag-function

WHEN passing line-break (\n) THEN the String.rawing it the backslash stays "visible" (and processable)

var expected = '\n'; assert.equal(String.raw`\n`, expected);

WHEN passing an escaped backslash to String.raw THEN this equals a string with two backslashes, where each is escaped

const TWO_BACKSLASHES = '\\'; assert.equal(String.raw`\\`, TWO_BACKSLASHES);

WHEN passing a unicode character THEN the leading backslash is made "visible"

var rawSmilie = '\u{1F600}'; const actual = String.raw`\u{1F600}`; assert.equal(actual, rawSmilie);

a use case: WHEN having a raw unicode character THEN I can modify it

const angryFace = '\u{1F620}'; const rawSmilie = String(`\u{1F600}`); const smilie = rawSmilie.replace('1F600', '1F620'); assert.equal(eval(`"${smilie}"`), angryFace);

GIVEN using String.raw as a function to call

WHEN String.raw() is called without a parameter THEN it throws

const callingStringRaw = () => String.raw; assert.throws(callingStringRaw, TypeError);

WHEN String.raw() is called with a string as parameter THEN it still throws

const callRawWithAString = () => String.raw({raw: 'a string'}); assert.throws(callRawWithAString, TypeError);

WHEN passing the first parameter {raw: []} THEN this equals to an empty string

const firstParam = {raw: undefined}; assert.equal(String.raw(firstParam), '');

WHEN passing the first property raw an array of strings THEN they are just concatenated

const expected = 'a,b,c'; assert.equal(String.raw({raw: ['a', 'b', 'c']}), expected);

WHEN passing more parameters, the substitutions THEN these are used as the filler between each raw string, in their according place

const rawStrings = ['-', '-']; assert.equal(String.raw({raw: rawStrings}, 1, 2), '.1-2.');

Links

spec The original official specification when introduced, it does not explain what this function does, but very much in detail how it works which results in explaining the "what" too.
spec The more readable and usable specification, in the version of the continuously maintained specification document.
mdn docs The Mozilla Developer Network docs, an easy to understand explanation.
video This video explains `String.raw` nicely by working with it on the browser console.

Required Knowledge

• basics (Arrow functions)
• `const` declaration (Block scope)
• as parameter (Rest operator)
• with arrays (Spread operator)

Related Katas

Template strings

• basics
• multiline
• tagged template strings
• raw property

String API

• string.includes()
• string.repeat(count)
• string.startsWith()
• string.endsWith()
• String.raw
• string.trimStart()
• string.matchAll()

Difficulty Level

ADVANCED

First Published

8 October 2023

Stats

9 tests to solve