refactor: Prevent reduce calls

eslint.config.js

@@ -231,6 +231,7 @@ const configs = antfu(
       }],
       'unicorn/explicit-length-check': 'error',
       'unicorn/new-for-builtins': 'error',
+      'unicorn/no-array-reduce': 'error',
       'unicorn/no-for-loop': 'error',
       'unicorn/no-invalid-remove-event-listener': 'error',
       'unicorn/no-lonely-if': 'error',
@@ -267,7 +268,6 @@ const configs = antfu(
       'unicorn/require-number-to-fixed-digits-argument': 'error',
 
       // Might want to enable these
-      'unicorn/no-array-reduce': 'off',
       'unicorn/no-array-for-each': 'off',
       'unicorn/no-await-expression-member': 'off',
       'unicorn/no-negated-condition': 'off',

src/authentication/UnionCredentialsExtractor.ts

@@ -14,12 +14,13 @@ export class UnionCredentialsExtractor extends UnionHandler<CredentialsExtractor
 
   public async combine(results: Credentials[]): Promise<Credentials> {
     // Combine all the results into a single object
-    return results.reduce((result, credentials): Credentials => {
-      for (const key of Object.keys(credentials) as (keyof Credentials)[]) {
-        this.setValue(result, key, credentials[key]);
+    const credentials: Credentials = {};
+    for (const result of results) {
+      for (const key of Object.keys(result) as (keyof Credentials)[]) {
+        this.setValue(credentials, key, result[key]);
       }
-      return result;
-    }, {});
+    }
+    return credentials;
   }
 
   /**

src/http/input/preferences/UnionPreferenceParser.ts

@@ -18,15 +18,16 @@ export class UnionPreferenceParser extends UnionHandler<PreferenceParser> {
       throw new InternalServerError('Found multiple range values. This implies a misconfiguration.');
     }
 
-    return results.reduce<RepresentationPreferences>((acc, val): RepresentationPreferences => {
-      for (const key of Object.keys(val) as (keyof RepresentationPreferences)[]) {
+    const preferences: RepresentationPreferences = {};
+    for (const result of results) {
+      for (const key of Object.keys(result) as (keyof RepresentationPreferences)[]) {
         if (key === 'range') {
-          acc[key] = val[key];
+          preferences[key] = result[key];
         } else {
-          acc[key] = { ...acc[key], ...val[key] };
+          preferences[key] = { ...preferences[key], ...result[key] };
         }
       }
-      return acc;
-    }, {});
+    }
+    return preferences;
   }
 }

src/server/util/RedirectingHttpHandler.ts

@@ -97,10 +97,10 @@ export class RedirectingHttpHandler extends HttpHandler {
 
     // Build redirect URL from regexp result
     const { match, redirectPattern } = result;
-    const redirect = match.reduce(
-      (prev, param, index): string => prev.replace(`$${index}`, param),
-      redirectPattern,
-    );
+    let redirect = redirectPattern;
+    for (const [ i, element ] of match.entries()) {
+      redirect = redirect.replace(`$${i}`, element);
+    }
 
     // Don't redirect if target is already correct
     if (redirect === target) {

src/storage/conversion/ChainedConverter.ts

@@ -188,13 +188,13 @@ export class ChainedConverter extends RepresentationConverter {
    * Will return undefined if there are no matches.
    */
   private findBest(paths: ConversionPath[]): ConversionPath | undefined {
-    // Need to use null instead of undefined so `reduce` doesn't take the first element of the array as `best`
-    return paths.reduce((best: ConversionPath | null, path): ConversionPath | null => {
+    let best: ConversionPath | undefined;
+    for (const path of paths) {
       if (path.weight > 0 && !(best && best.weight >= path.weight)) {
-        return path;
+        best = path;
+      }
     }
     return best;
-    }, null) ?? undefined;
   }
 
   /**

src/storage/conversion/ConversionUtil.ts

@@ -113,20 +113,20 @@ export function getWeightedPreferences(types: ValuePreferences, preferred: Value
  * Undefined if there is no match.
  */
 export function getBestPreference(types: ValuePreferences, preferred: ValuePreferences): ValuePreference | undefined {
-  // Could also return the first entry of the above function but this is more efficient
-  const result = Object.entries(types).reduce((best, [ value, quality ]): ValuePreference => {
+  // Could also return the first entry of `getWeightedPreferences` but this is more efficient
+  let best: ValuePreference = { value: '', weight: 0 };
+  for (const [ value, quality ] of Object.entries(types)) {
     if (best.weight >= quality) {
-      return best;
+      continue;
     }
     const weight = quality * getTypeWeight(value, preferred);
     if (weight > best.weight) {
-      return { value, weight };
+      best = { value, weight };
+    }
   }
-    return best;
-  }, { value: '', weight: 0 });
 
-  if (result.weight > 0) {
-    return result;
+  if (best.weight > 0) {
+    return best;
   }
 }
 

src/storage/keyvalue/WrappedIndexedStorage.ts

@@ -526,7 +526,11 @@ export class WrappedIndexedStorage<T extends IndexTypeCollection<T>> implements
       indexResults.push(rootIds);
     }
 
-    return indexResults.reduce((acc, ids): string[] => acc.filter((id): boolean => ids.includes(id)));
+    let indexedRoots: string[] = indexResults[0];
+    for (const ids of indexResults.slice(1)) {
+      indexedRoots = indexedRoots.filter((id): boolean => ids.includes(id));
+    }
+    return indexedRoots;
   }
 
   /**
@@ -581,9 +585,13 @@ export class WrappedIndexedStorage<T extends IndexTypeCollection<T>> implements
     }
 
     // For all keys that were not handled recursively: make sure that it matches the found objects
-    const remainingKeys = Object.keys(query).filter((key): boolean =>
-      key !== relation?.child.key || typeof query[key] === 'string');
-    return remainingKeys.reduce((acc, key): any[] => acc.filter((obj): boolean => obj[key] === query[key]), objs);
+    const remainingKeys = Object.keys(query).filter(
+      (key): boolean => key !== relation?.child.key || typeof query[key] === 'string',
+    );
+    for (const key of remainingKeys) {
+      objs = objs.filter((obj): boolean => obj[key] === query[key]);
+    }
+    return objs;
   }
 
   // --------------------------------- INDEX HELPERS ---------------------------------

src/storage/size-reporter/FileSizeReporter.ts

@@ -71,17 +71,16 @@ export class FileSizeReporter implements SizeReporter<string> {
     const childFiles = await fsPromises.readdir(fileLocation);
     const rootFilePathLength = trimTrailingSlashes(this.rootFilePath).length;
 
-    return await childFiles.reduce(async(acc: Promise<number>, current): Promise<number> => {
+    let totalSize = stat.size;
+    for (const current of childFiles) {
       const childFileLocation = normalizeFilePath(joinFilePath(fileLocation, current));
-      let result = await acc;
 
       // Exclude internal files
       if (!this.ignoreFolders.some((folder: RegExp): boolean =>
         folder.test(childFileLocation.slice(rootFilePathLength)))) {
-        result += await this.getTotalSize(childFileLocation);
-      }
-
-      return result;
-    }, Promise.resolve(stat.size));
+        totalSize += await this.getTotalSize(childFileLocation);
+      }
+    }
+    return totalSize;
   }
 }

src/util/Header.ts

@@ -58,9 +58,10 @@ export class ContentType {
    * @returns The value string, including parameters, if present.
    */
   public toHeaderValueString(): string {
-    return Object.entries(this.parameters)
+    const parameterStrings = Object.entries(this.parameters)
       .sort((entry1, entry2): number => entry1[0].localeCompare(entry2[0]))
-      .reduce((acc, entry): string => `${acc}; ${entry[0]}=${entry[1]}`, this.value);
+      .map(([ key, value ]): string => `${key}=${value}`);
+    return [ this.value, ...parameterStrings ].join('; ');
   }
 }
 

src/util/HeaderUtil.ts

@@ -111,7 +111,8 @@ function handleInvalidValue(message: string, strict: boolean): void | never {
  */
 export function parseParameters(parameters: string[], replacements: Record<string, string>, strict = false):
 { name: string; value: string }[] {
-  return parameters.reduce<{ name: string; value: string }[]>((acc, param): { name: string; value: string }[] => {
+  const parsed: { name: string; value: string }[] = [];
+  for (const param of parameters) {
     const [ name, rawValue ] = param.split('=').map((str): string => str.trim());
 
     // Test replaced string for easier check
@@ -120,7 +121,7 @@ export function parseParameters(parameters: string[], replacements: Record<strin
     if (!(TOKEN.test(name) && (!rawValue || /^"\d+"$/u.test(rawValue) || TOKEN.test(rawValue)))) {
       handleInvalidValue(`Invalid parameter value: ${name}=${replacements[rawValue] || rawValue} ` +
         `does not match (token ( "=" ( token / quoted-string ))?). `, strict);
-      return acc;
+      continue;
     }
 
     let value = rawValue;
@@ -128,9 +129,9 @@ export function parseParameters(parameters: string[], replacements: Record<strin
       value = replacements[rawValue];
     }
 
-    acc.push({ name, value });
-    return acc;
-  }, []);
+    parsed.push({ name, value });
+  }
+  return parsed;
 }
 
 // eslint-disable-next-line jsdoc/require-returns-check
@@ -239,17 +240,15 @@ export function parseAccept(input: string, strict = false): Accept[] {
   // Quoted strings could prevent split from having correct results
   const { result, replacements } = transformQuotedStrings(input);
 
-  return splitAndClean(result)
-    .reduce<Accept[]>((acc, part): Accept[] => {
+  const accepts: Accept[] = [];
+  for (const part of splitAndClean(result)) {
     const partOrUndef = parseAcceptPart(part, replacements, strict);
 
     if (partOrUndef !== undefined) {
-        acc.push(partOrUndef);
+      accepts.push(partOrUndef);
     }
-
-      return acc;
-    }, [])
-    .sort((left, right): number => right.weight - left.weight);
+  }
+  return accepts.sort((left, right): number => right.weight - left.weight);
 }
 
 /**
@@ -384,14 +383,11 @@ export function parseContentType(input: string): ContentType {
     throw new BadRequestHttpError(`Invalid content-type: ${value} does not match ( token "/" token )`);
   }
 
-  return parseParameters(params, replacements)
-    .reduce<ContentType>(
-      (prev, cur): ContentType => {
-        prev.parameters[cur.name] = cur.value;
-        return prev;
-      },
-      new ContentType(value),
-    );
+  const contentType = new ContentType(value);
+  for (const param of parseParameters(params, replacements)) {
+    contentType.parameters[param.name] = param.value;
+  }
+  return contentType;
 }
 
 /**

src/util/QuadUtil.ts

@@ -37,12 +37,13 @@ export async function parseQuads(readable: Guarded<Readable>, options: ParserOpt
  * @returns A new array containing the unique quads.
  */
 export function uniqueQuads(quads: Quad[]): Quad[] {
-  return quads.reduce<Quad[]>((result, quad): Quad[] => {
-    if (!result.some((item): boolean => quad.equals(item))) {
-      result.push(quad);
+  const uniques: Quad[] = [];
+  for (const quad of quads) {
+    if (!uniques.some((item): boolean => quad.equals(item))) {
+      uniques.push(quad);
     }
-    return result;
-  }, []);
+  }
+  return uniques;
 }
 
 /**

src/util/errors/HttpErrorUtil.ts

@@ -34,12 +34,14 @@ export function errorTermsToMetadata(terms: Dict<string>, metadata?: Representat
  * @param metadata - Metadata to extract the terms from.
  */
 export function extractErrorTerms(metadata: RepresentationMetadata): Dict<string> {
-  return metadata.quads()
-    .filter((quad): boolean => quad.predicate.value.startsWith(SOLID_ERROR_TERM.namespace))
-    .reduce<NodeJS.Dict<string>>((acc, quad): Dict<string> => {
-      acc[quad.predicate.value.slice(SOLID_ERROR_TERM.namespace.length)] = quad.object.value;
-      return acc;
-    }, {});
+  const errorQuads = metadata.quads()
+    .filter((quad): boolean => quad.predicate.value.startsWith(SOLID_ERROR_TERM.namespace));
+
+  const errorTerms: Dict<string> = {};
+  for (const quad of errorQuads) {
+    errorTerms[quad.predicate.value.slice(SOLID_ERROR_TERM.namespace.length)] = quad.object.value;
+  }
+  return errorTerms;
 }
 
 /**