return default index when not found

snippets/findLastIndex.md

@@ -4,15 +4,17 @@ Returns the index of the last element for which the provided function returns a
 
 Use `Array.prototype.map()` to map each element to an array with its index and value.
 Use `Array.prototype.filter()` to remove elements for which `fn` returns falsy values, `Array.prototype.pop()` to get the last one.
+`-1` is the default value when not found.
 
 ```js
 const findLastIndex = (arr, fn) =>
-  arr
+  (arr
     .map((val, i) => [i, val])
     .filter(([i, val]) => fn(val, i, arr))
-    .pop()[0];
+    .pop() || [-1])[0];
 ```
 
 ```js
 findLastIndex([1, 2, 3, 4], n => n % 2 === 1); // 2 (index of the value 3)
+findLastIndex([1, 2, 3, 4], n => n === 5); // -1 (default value when not found)
 ```

test/_30s.js

@@ -364,10 +364,10 @@ const filterNonUniqueBy = (arr, fn) =>
 const findKey = (obj, fn) => Object.keys(obj).find(key => fn(obj[key], key, obj));
 const findLast = (arr, fn) => arr.filter(fn).pop();
 const findLastIndex = (arr, fn) =>
-  arr
+  (arr
     .map((val, i) => [i, val])
     .filter(([i, val]) => fn(val, i, arr))
-    .pop()[0];
+    .pop() || [-1])[0];
 const findLastKey = (obj, fn) =>
   Object.keys(obj)
     .reverse()
@@ -1547,4 +1547,4 @@ const speechSynthesis = message => {
 const squareSum = (...args) => args.reduce((squareSum, number) => squareSum + Math.pow(number, 2), 0);
 
 
-module.exports = {CSVToArray,CSVToJSON,JSONToFile,JSONtoCSV,RGBToHex,URLJoin,UUIDGeneratorBrowser,UUIDGeneratorNode,all,allEqual,any,approximatelyEqual,arrayToCSV,arrayToHtmlList,ary,atob,attempt,average,averageBy,bifurcate,bifurcateBy,bind,bindAll,bindKey,binomialCoefficient,bottomVisible,btoa,byteSize,call,capitalize,capitalizeEveryWord,castArray,chainAsync,checkProp,chunk,clampNumber,cloneRegExp,coalesce,coalesceFactory,collectInto,colorize,compact,compactWhitespace,compose,composeRight,converge,copyToClipboard,countBy,countOccurrences,counter,createDirIfNotExists,createElement,createEventHub,currentURL,curry,dayOfYear,debounce,decapitalize,deepClone,deepFlatten,deepFreeze,deepGet,deepMapKeys,defaults,defer,degreesToRads,delay,detectDeviceType,difference,differenceBy,differenceWith,dig,digitize,distance,drop,dropRight,dropRightWhile,dropWhile,elementContains,elementIsVisibleInViewport,elo,equals,escapeHTML,escapeRegExp,everyNth,extendHex,factorial,fibonacci,filterFalsy,filterNonUnique,filterNonUniqueBy,findKey,findLast,findLastIndex,findLastKey,flatten,flattenObject,flip,forEachRight,forOwn,forOwnRight,formToObject,formatDuration,fromCamelCase,functionName,functions,gcd,geometricProgression,get,getColonTimeFromDate,getDaysDiffBetweenDates,getImages,getMeridiemSuffixOfInteger,getScrollPosition,getStyle,getType,getURLParameters,groupBy,hammingDistance,hasClass,hasFlags,hashBrowser,hashNode,head,hexToRGB,hide,httpGet,httpPost,httpsRedirect,hz,inRange,indentString,indexOfAll,initial,initialize2DArray,initializeArrayWithRange,initializeArrayWithRangeRight,initializeArrayWithValues,initializeNDArray,insertAfter,insertBefore,intersection,intersectionBy,intersectionWith,invertKeyValues,is,isAbsoluteURL,isAfterDate,isAnagram,isArrayLike,isBeforeDate,isBoolean,isBrowser,isBrowserTabFocused,isDivisible,isDuplexStream,isEmpty,isEven,isFunction,isLowerCase,isNegativeZero,isNil,isNull,isNumber,isObject,isObjectLike,isPlainObject,isPrime,isPrimitive,isPromiseLike,isReadableStream,isSameDate,isSorted,isStream,isString,isSymbol,isTravisCI,isUndefined,isUpperCase,isValidJSON,isWeekday,isWeekend,isWritableStream,join,last,lcm,longestItem,lowercaseKeys,luhnCheck,mapKeys,mapNumRange,mapObject,mapString,mapValues,mask,matches,matchesWith,maxBy,maxDate,maxN,median,memoize,merge,midpoint,minBy,minDate,minN,mostPerformant,negate,nest,nodeListToArray,none,nthArg,nthElement,objectFromPairs,objectToPairs,observeMutations,off,offset,omit,omitBy,on,onUserInputChange,once,orderBy,over,overArgs,pad,palindrome,parseCookie,partial,partialRight,partition,percentile,permutations,pick,pickBy,pipeAsyncFunctions,pipeFunctions,pluralize,powerset,prefix,prettyBytes,primes,promisify,pull,pullAtIndex,pullAtValue,pullBy,radsToDegrees,randomHexColorCode,randomIntArrayInRange,randomIntegerInRange,randomNumberInRange,readFileLines,rearg,recordAnimationFrames,redirect,reduceSuccessive,reduceWhich,reducedFilter,reject,remove,removeNonASCII,renameKeys,reverseString,round,runAsync,runPromisesInSeries,sample,sampleSize,scrollToTop,sdbm,serializeCookie,serializeForm,setStyle,shallowClone,shank,show,shuffle,similarity,size,sleep,smoothScroll,sortCharactersInString,sortedIndex,sortedIndexBy,sortedLastIndex,sortedLastIndexBy,splitLines,spreadOver,stableSort,standardDeviation,stringPermutations,stripHTMLTags,sum,sumBy,sumPower,symmetricDifference,symmetricDifferenceBy,symmetricDifferenceWith,tail,take,takeRight,takeRightWhile,takeWhile,throttle,timeTaken,times,toCamelCase,toCurrency,toDecimalMark,toHash,toKebabCase,toOrdinalSuffix,toSafeInteger,toSnakeCase,toTitleCase,toggleClass,tomorrow,transform,triggerEvent,truncateString,truthCheckCollection,unary,uncurry,unescapeHTML,unflattenObject,unfold,union,unionBy,unionWith,uniqueElements,uniqueElementsBy,uniqueElementsByRight,uniqueSymmetricDifference,untildify,unzip,unzipWith,validateNumber,vectorDistance,when,without,words,xProd,yesNo,yesterday,zip,zipObject,zipWith,JSONToDate,binarySearch,celsiusToFahrenheit,cleanObj,collatz,countVowels,factors,fahrenheitToCelsius,fibonacciCountUntilNum,fibonacciUntilNum,heronArea,howManyTimes,httpDelete,httpPut,isArmstrongNumber,isSimilar,kmphToMph,levenshteinDistance,mphToKmph,pipeLog,quickSort,removeVowels,solveRPN,speechSynthesis,squareSum}
+module.exports = {CSVToArray,CSVToJSON,JSONToFile,JSONtoCSV,RGBToHex,URLJoin,UUIDGeneratorBrowser,UUIDGeneratorNode,all,allEqual,any,approximatelyEqual,arrayToCSV,arrayToHtmlList,ary,atob,attempt,average,averageBy,bifurcate,bifurcateBy,bind,bindAll,bindKey,binomialCoefficient,bottomVisible,btoa,byteSize,call,capitalize,capitalizeEveryWord,castArray,chainAsync,checkProp,chunk,clampNumber,cloneRegExp,coalesce,coalesceFactory,collectInto,colorize,compact,compactWhitespace,compose,composeRight,converge,copyToClipboard,countBy,countOccurrences,counter,createDirIfNotExists,createElement,createEventHub,currentURL,curry,dayOfYear,debounce,decapitalize,deepClone,deepFlatten,deepFreeze,deepGet,deepMapKeys,defaults,defer,degreesToRads,delay,detectDeviceType,difference,differenceBy,differenceWith,dig,digitize,distance,drop,dropRight,dropRightWhile,dropWhile,elementContains,elementIsVisibleInViewport,elo,equals,escapeHTML,escapeRegExp,everyNth,extendHex,factorial,fibonacci,filterFalsy,filterNonUnique,filterNonUniqueBy,findKey,findLast,findLastIndex,findLastKey,flatten,flattenObject,flip,forEachRight,forOwn,forOwnRight,formToObject,formatDuration,fromCamelCase,functionName,functions,gcd,geometricProgression,get,getColonTimeFromDate,getDaysDiffBetweenDates,getImages,getMeridiemSuffixOfInteger,getScrollPosition,getStyle,getType,getURLParameters,groupBy,hammingDistance,hasClass,hasFlags,hashBrowser,hashNode,head,hexToRGB,hide,httpGet,httpPost,httpsRedirect,hz,inRange,indentString,indexOfAll,initial,initialize2DArray,initializeArrayWithRange,initializeArrayWithRangeRight,initializeArrayWithValues,initializeNDArray,insertAfter,insertBefore,intersection,intersectionBy,intersectionWith,invertKeyValues,is,isAbsoluteURL,isAfterDate,isAnagram,isArrayLike,isBeforeDate,isBoolean,isBrowser,isBrowserTabFocused,isDivisible,isDuplexStream,isEmpty,isEven,isFunction,isLowerCase,isNegativeZero,isNil,isNull,isNumber,isObject,isObjectLike,isPlainObject,isPrime,isPrimitive,isPromiseLike,isReadableStream,isSameDate,isSorted,isStream,isString,isSymbol,isTravisCI,isUndefined,isUpperCase,isValidJSON,isWeekday,isWeekend,isWritableStream,join,last,lcm,longestItem,lowercaseKeys,luhnCheck,mapKeys,mapNumRange,mapObject,mapString,mapValues,mask,matches,matchesWith,maxBy,maxDate,maxN,median,memoize,merge,midpoint,minBy,minDate,minN,mostPerformant,negate,nest,nodeListToArray,none,nthArg,nthElement,objectFromPairs,objectToPairs,observeMutations,off,offset,omit,omitBy,on,onUserInputChange,once,orderBy,over,overArgs,pad,palindrome,parseCookie,partial,partialRight,partition,percentile,permutations,pick,pickBy,pipeAsyncFunctions,pipeFunctions,pluralize,powerset,prefix,prettyBytes,primes,promisify,pull,pullAtIndex,pullAtValue,pullBy,radsToDegrees,randomHexColorCode,randomIntArrayInRange,randomIntegerInRange,randomNumberInRange,readFileLines,rearg,recordAnimationFrames,redirect,reduceSuccessive,reduceWhich,reducedFilter,reject,remove,removeNonASCII,renameKeys,reverseString,round,runAsync,runPromisesInSeries,sample,sampleSize,scrollToTop,sdbm,serializeCookie,serializeForm,setStyle,shallowClone,shank,show,shuffle,similarity,size,sleep,smoothScroll,sortCharactersInString,sortedIndex,sortedIndexBy,sortedLastIndex,sortedLastIndexBy,splitLines,spreadOver,stableSort,standardDeviation,stringPermutations,stripHTMLTags,sum,sumBy,sumPower,symmetricDifference,symmetricDifferenceBy,symmetricDifferenceWith,tail,take,takeRight,takeRightWhile,takeWhile,throttle,timeTaken,times,toCamelCase,toCurrency,toDecimalMark,toHash,toKebabCase,toOrdinalSuffix,toSafeInteger,toSnakeCase,toTitleCase,toggleClass,tomorrow,transform,triggerEvent,truncateString,truthCheckCollection,unary,uncurry,unescapeHTML,unflattenObject,unfold,union,unionBy,unionWith,uniqueElements,uniqueElementsBy,uniqueElementsByRight,uniqueSymmetricDifference,untildify,unzip,unzipWith,validateNumber,vectorDistance,when,without,words,xProd,yesNo,yesterday,zip,zipObject,zipWith,JSONToDate,binarySearch,celsiusToFahrenheit,cleanObj,collatz,countVowels,factors,fahrenheitToCelsius,fibonacciCountUntilNum,fibonacciUntilNum,heronArea,howManyTimes,httpDelete,httpPut,isArmstrongNumber,isSimilar,kmphToMph,levenshteinDistance,mphToKmph,pipeLog,quickSort,removeVowels,solveRPN,speechSynthesis,squareSum}

test/findLastIndex.test.js

@@ -6,3 +6,6 @@ test('findLastIndex is a Function', () => {
 test('Finds last index for which the given function returns true', () => {
   expect(findLastIndex([1, 2, 3, 4], n => n % 2 === 1)).toBe(2);
 });
+test('Return default index when not found', () => {
+  expect(findLastIndex([1, 2, 3, 4], n => n === 5)).toBe(-1);
+});