Returns the last element for which the provided function returns a truthy value.
Use Array.prototype.filter() to remove elements for which fn returns falsy values, Array.prototype.pop() to get the last one.
const findLast = (arr, fn) => arr.filter(fn).pop();
findLast([1, 2, 3, 4], n => n % 2 === 1); // 3 -
Returns the index of the last element for which the provided function returns a truthy value.
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.
const findLastIndex = (arr, fn) => - arr +
Returns the index of the last element for which the provided function returns a truthy value.
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.
const findLastIndex = (arr, fn) => + (arr .map((val, i) => [i, val]) .filter(([i, val]) => fn(val, i, arr)) - .pop()[0]; + .pop() || [-1])[0];
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)
Flattens an array up to the specified depth.
Use recursion, decrementing depth by 1 for each level of depth. Use Array.prototype.reduce() and Array.prototype.concat() to merge elements or arrays. Base case, for depth equal to 1 stops recursion. Omit the second argument, depth to flatten only to a depth of 1 (single flatten).
const flatten = (arr, depth = 1) => arr.reduce((a, v) => a.concat(depth > 1 && Array.isArray(v) ? flatten(v, depth - 1) : v), []);
flatten([1, [2], 3, 4]); // [1, 2, 3, 4] diff --git a/snippets/checkProp.md b/snippets/checkProp.md index 5b76c6b3e..af0f5bdd0 100644 --- a/snippets/checkProp.md +++ b/snippets/checkProp.md @@ -24,6 +24,7 @@ const checkProp = (predicate, prop) => obj => !!predicate(obj[prop]); + const lengthIs4 = checkProp(l => l === 4, 'length'); lengthIs4([]); // false lengthIs4([1,2,3,4]); // true diff --git a/test/_30s.js b/test/_30s.js index ffe93527a..0ef0fca37 100644 --- a/test/_30s.js +++ b/test/_30s.js @@ -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} \ No newline at end of file