UnderscoreJS - The Master Guide

Discover the UnderscoreJS arrays and collections module, explore over 40 functions for manipulating arrays and collections, and kick off the first module with practical examples.

Explore how underscore's collection methods operate on any collection, while array methods require a true array, clarifying the distinction for effective use.

Explore iterating arrays and objects with underscore forEach and native JavaScript forEach, comparing outputs, chaining results, and building a simple jukebox using track data.

Test your knowledge of the forEach method by implementing a jukebox player that outputs each song title to the console, enumerating through the song list with an arrow function.

Discover how the pluck function extracts a single property from an array of objects by passing the array and the property name as a string; for multiple properties, use map.

Map arrays and collections by pulling multiple properties from objects, using arrow functions and the map alias collect; aggregate ages and access item indices.

Apply map function to convert a user list into objects with a name by concatenating first name and last name, and a code_status online when active is true, otherwise offline.

Explore mapping techniques to transform a users array into objects with first name, last name, and online status by checking an active flag, using map or area function.

Learn how to extract values from arrays with UnderscoreJS using first, last, initial, and rest, including optional counts and their aliases like head, take, tell, and drop.

Master data filtering with underscorejs by applying conditions to return subsets, using filter or alias select to get totals above a threshold and recent years (2016–2017).

Learn to filter by multiple properties with where, combining area and year, and use find where to fetch the first match; compare with filter for broader conditions.

Explore how underscore's find (detect) returns the first list item that meets a condition, using the active flag or age greater than 10 to locate users like Bonnie.

Explore how reduce and reduceRight collapse an array to a single value by applying a function with an accumulator and an optional initial value; compare left-to-right and right-to-left processing.

Learn to shuffle a list of music tracks by calling the shuffle method, which returns a different randomized order for the playlist each time you invoke it.

Use the sample function to select a random item or multiple items from a list of objects, such as total sales, and return varied random selections.

Learn how the size function counts items in arrays, characters in strings, and properties on objects, offering a quick alternative to the length property.

Discover how UnderscoreJS indexOf and lastIndexOf locate values in arrays, compare to native methods, use the extra parameter for binary search on sorted arrays, and boost search performance.

Utilize the sorted index method in UnderscoreJS to locate the insertion point for a new value using binary search, even in object arrays by a chosen property.

Explore how findIndex and findLastIndex use predicate functions to locate items in an array of objects, returning the first or last matching index and supporting complex conditions.

Pull the minimum and maximum values from an array using the min and max methods, applicable to numbers and floats, delivering quick, convenient results.

Apply the reverse function to arrays to flip numbers and letters, returning them in reverse order with speed and simplicity.

Learn how to use UnderscoreJS filter and reject to handle a condition on total cells, selecting totals equal or greater than 100 and returning those that don't meet it.

Explains using underscorejs every and some to test conditions on yearly sales totals; every checks all values meet (>=100), while some checks if any do, with aliases every/or and some/eddie.

Learn how to determine if a value exists in an array using the contains method, which returns true or false, instead of an index, with the aliases includes and include.

The invoker method runs a named function on each value in a list, enabling sorting numeric arrays, joining string arrays with a delimiter, and applying custom functions.

Sort by year or area, group by area, and index by using Underscore's methods; compare group by and index by structures and count by to create summary reports.

Discover the toArray function in UnderscoreJS master guide, converting objects, strings, and function arguments into arrays with examples from a simple object, a string, and an immediately invoked function.

Split a collection into passing and failing groups using underscore's partition, replacing separate filter and reject calls, with active status and age-based examples.

Learn how the compact method in UnderscoreJS cleans arrays by removing undefined, null, empty values, and even zeros, returning a new cleaned array, though it can be overzealous.

Learn how UnderscoreJS flattens nested arrays into a single level with the flatten method, which flattens recursively by default and accepts a second parameter to limit depth.

Learn to remove specified values from an array using the underscore.js without method. Pass the array and the values to remove to obtain the remaining elements, as shown in examples.

Explore union, intersection, and difference for arrays: union merges arrays with duplicates removed, intersection finds elements in all arrays, and difference reveals elements unique to the first array.

Learn to remove duplicate numbers from an array in JavaScript using Underscore's uniq method and its alias unique. The example shows 4 and 8 removed, returning a deduplicated array.

Explore how zip groups elements from multiple arrays into paired columns and how unzip restores them to the original arrays, handling uneven lengths and undefined values.

Learn how to convert two arrays into an object using underscore's object method, with last-write-wins behavior on duplicates, and apply it to realistic keys like user ids or track ids.

Split a large binary file into chunks with underscore's chunk method, then process and upload each chunk to an API in a loop; note the last chunk may be smaller.

Apply the UnderscoreJS range method to generate an array of numbers from a start value to a stop value, not including stop, with an optional step.

Explore how to manipulate functions with underscore's 15 functions, focusing on throttling, debasing and memorize functions, plus defer and delay for web development.

Learn how Underscore's bind method binds this to a target object, letting a print function access an object's x and y properties and produce prefixed outputs instead of undefined.

Explore binding techniques in underscore: bind and bindAll attach a function to an object, preserving context and enabling aliases, demonstrated with a sheep blueprint.

Learn to use a partial function to pre-fill known parameters and arguments, create cleaner code, and employ placeholders to control which ones are supplied.

This lecture demonstrates using underscore's memorize (memoize) to cache function results, keep data like stock prices fresh, and manually update or clear the cache when underlying values change.

Discover how to use the delay method to postpone function execution by a set millisecond delay, compare it to native JavaScript, and use console.log with template strings and arrow functions.

Learn to defer function execution with underscore's defer, easier than setTimeout, to run after the current call stack clears, often to focus page elements after render.

Learn how the underscore throttle method restricts a function's calls to a rate, firing immediately or after a delay, and limiting to once every 10 seconds to prevent API overload.

Explore how debounce protects API calls by waiting for user to stop typing before executing, using setTimeout with a five-second delay in a practical auto-suggest example.

Explore how Underscore's once memoizes a function to run only once, and how before and after control invocation counts, enabling up to five calls with memorized values.

Discover how to use the underscore wrap method to create a wrapper around a function, enabling before and after code with examples like squaring a value and html escaping.

Learn how the UnderscoreJS negate method reverses the result of any function, using map on arrays to flip true/false outcomes and simplify selecting when conditions are not met.

Explore composing a sequence of functions into a single composite function that passes each function's output as the next input, demonstrating reverse order execution and practical aggregation of calculations.

Learn how rest arguments collect remaining inputs in JavaScript functions, using rest parameters to handle multiple values, with template strings and arrow syntax examples.

Explore how underscore helps manipulate objects in JavaScript by assigning, merging, updating, and picking properties. Learn type checks, conversions, defaults, and fast, consistent methods for JSON data and APIs.

Extract property names with keys, values with values, and name-value pairs with pairs from an object using underscore, and use all keys to reveal inherited properties from the prototype.

Learn how to use underscore's invert method to swap object keys and values, demonstrated on a user object where body becomes a key and id becomes a value.

Learn to create a vehicle blueprint and a car object that inherits properties using underscore's create method, linking prototypes to ensure correct inheritance and instance checks.

Learn to list all available methods on an object using functions and aliases; see a sample object with Joy and Break and the array of names break and drive.

Learn to locate the next unplayed track in a jukebox-style object using UnderscoreJS findKey and a unique key, returning the first key with play set to false.

Extend merges properties from source objects into a destination object using Underscore, with source values taking precedence over destination properties, and supports multiple source objects.

Explore how extend own differs from extend by building a vehicle and a car, then adding a make property, showing that extend own adds only specified properties, not inherited ones.

Learn to secure API responses by using pick and omit to return only permitted properties, avoiding internal ones, and optionally filter by type with predicates.

Learn how the defaults method populates undefined properties on objects, how to override fields, and see examples with car, bicycle, and horse drawn carriage.

The lecture demonstrates cloning objects with the clone method, creating independent copies for shallow properties, while showing that deep properties are copied by reference, not by value.

Learn how map computes percentages from royalties across a total, and how map object returns year-keyed results, making it easier to associate years with values.

Discover the two path utility in UnderscoreJS, which validates and converts paths to arrays for get operations; learn to access deep properties with bracketed comma-separated paths and overrides via mixin.

Learn how to check for a property's existence with has, and retrieve values with get, using property keys and property paths for nested objects and arrays, including default values.

Learn how to use property and propertyOf in UnderscoreJS to extract values from single objects and arrays, comparing get and map approaches for clean, concise code.

Learn how the isEqual method compares two objects by recursively checking all properties and values, including deep objects, to confirm equality even when references differ.

Learn to build predicate functions with the underscorejs matcher to filter collections by exact property values, such as active flag and age, using absolute comparisons only and not-equal not supported.

Use isMatch to check a single object's id property, returning true when id equals 10 and false otherwise, contrasting with matches that operate on a collection.

Explore underscore's is undefined, is null, is empty, and is none checks, and see how they handle strings, objects, arrays, and numbers, with a note on native versus undiscovered versions.

Explore underscore's primitive type checks, including is string, is boolean, is date, and is number. See practical true/false examples.

Discover type checking methods for structures and buffers, including isArray, isTypedArray, isMap, isWeakMap, isSet, isWeakSet, isArrayBuffer, and isDataView. Learn how each validates its specific type.

Explore the utilities group in underscorejs, including arguments, is simple (symbol), is object, is function, is regular expression, is error, is elements (dom element), and is finite.

Explore the utility functions in Underscore, including templates and mixing unique codes, as you begin this small but useful module and its first lecture.

Learn to prevent library conflicts by using noConflict with the underscore library; it returns a handle you can assign to another variable, then call underscore methods alongside other libraries.

Explore the identity function in underscore, a no transformation placeholder that returns input. It serves as the default iteratee for sorting and guides find by returning the first matching entry.

Learn how the UnderscoreJS times method repeats an action a set number of times without a list, calling a function (like console log or an API call) for each iteration.

Explore underscore's constant function to return a fixed value for initializing arrays or neural network weights, and use the random function to generate 0–9 values, scaled to 0–1 with times.

Learn to extend underscore with a mixin plugin by defining a capitalize function. Use the mixin method to add this function, which capitalizes the first character and lowercases the rest.

Explore how underscore uses an iteratee callback to process every collection element with the filter method. Define the filter upfront to reuse across arrays, improving code readability and reducing repetition.

Learn how the UnderscoreJS escape and unescape functions encode and decode HTML entities to prevent malicious input; encode ampersand, greater-than, less-than, single and double quotes, then decode back.

Learn how result methods let you retrieve values from an object whether a property or a function, without worrying about when a value is calculated.

Use the underscore.js now method to obtain milliseconds since the epoch, January 1, 1970, and compare it with date.now() for timing and animation, noting potential performance gains.

Generate unique, auto-incrementing ids for dom elements with underscore's uniqueId function; optionally add a prefix like 'user_' to distinguish ui elements in web pages.

Explore the templates function, a powerful string function that substitutes data with interpolation limiters, shows template and print examples, and explains H2 model emitters and escaping.

Explore sequencing and chaining in Underscore, build your first chain, and learn keywords like chain value and tap to create complex queries before obtaining the final value.

Explore how chaining with underscore transforms array manipulation into a clean, lazy, functional process by combining filter, unique, and map, and contrast it with working without any chaining.

Discover how chaining works by passing wrapped data through a sequence of functions such as union, filter, unique, and map, with lazy evaluation via the chain and dot value.

Build a chain to identify the sales entry with the highest total in 2016 using underscore methods. Explore variations in the next video to cement your understanding of chaining.

Chain total cells, sort by the total property in ascending order, and take the last entry to get 2016; or reverse and take the first.

Explore how the tap method in a chain sequence intercepts and manipulates intermediate results, using arrays with reverse, head, pop, and push to modify values before final output.

Explore the underscore core library’s 100 functions and an essential add-on with extra utilities for web development, including phi-dash, arise, and humanise words.

Learn to install the underscore dot string library as an add-on to underscore by adding an extra require line; discover its documentation via Google search and explore the available functions.

Format large numbers with underscore string's format function to apply thousands separators and two decimal places, with customizable decimal and thousand separators for international numbers.

Explore underscore string function Levenstein, which calculates the distance between two strings and shows that lower scores indicate greater similarity.

Explore the underscore string add on case-changing methods, including capitalize, decapitalize, swap case, titleize, and camelize, and see how they adjust capitalization across strings.

Explore UnderscoreJS functions starts with, ends with, is blank, and includes, with practical demos using a Sony Bravia TV string to illustrate start, end, blank checks, and substring inclusion.

Explore escape HTML and unescape HTML functions that convert characters to and from HTML entities. Apply these techniques to safe rich text editing and storing HTML markup in databases.

Learn how to manipulate strings with classify, underscored, dasherize, and humanize to generate class names, convert camel case to underscores or dashes, and create human-friendly text.

Explore the underscored string library's trim methods to remove spaces and other characters from strings. Learn how trim, ltrim, rtrim, and clean behave, including defaults, custom characters, and space normalization.

Explore underscorejs's successor and predecessor functions, which return the next or previous ASCII character for letters and symbols, illustrated with A to B, F to G, and the backtick.

Explore underscore string functions chop and chars, which split a string into substrings by length and into single characters. See examples with hello world and varying lengths.

Explore the underscore string function reverse, which reverses a given string. See examples with hello and good morning, demonstrating simple, quick results.

Count tallies how many times a substring appears in a string. In 'hello world', the letter l appears three times, and 'end' in 'banana' appears twice.

Learn how the slugify function from the underscore add-on converts strings to URL friendly, lowercase text by removing spaces, special characters, and diacritics for search engine friendly slugs.

Explore the quote and unquote functions to wrap and remove quotes from strings. See how default double quotes can be overridden with single quotes.

Learn how the repeat function duplicates a string a specified number of times, with an optional separator to join repeats, demonstrated with apple, pear, and hyphen or plus.

Explore the underscore string function surround, which wraps a given string with another string on both sides. See examples using hello with asterisks and percent signs.

Learn two string utilities: strip tags to remove html and script tags for security, and clean diacritics to remove diacritical marks for simplified text.

Learn to join strings with a separator to combine multiple inputs, using spaces, hyphens, or multicharacter delimiters. Use splice to insert a substring at a specific index, replacing characters.

Learn to split strings into lines and words with UnderscoreJS by using newline characters or spaces, customizing delimiters, using regular expressions, and handling empty inputs.

Explore the insert and replace all functions in underscorejs, learning how to insert substrings at given indices (including negative and boundary cases) and replace all occurrences with optional case-insensitive parameters.

Explore the underscore string map function, which creates a new string by applying a function to each character. See examples of shifting characters via ASCII and converting to uppercase.

Learn how the underscore js toNumber and toBoolean helpers convert strings to numbers and booleans, with optional decimal places, rounding, and customizable truthy or falsy mappings.

Explore the toSentence and toSentenceSerial functions that join an array of words into a human readable sentence, with customizable separators and final conjunctions.

Explore underscorejs string searching with strLeft, strRight, strLeftBack, and strRightBack that take a source string and a pattern and return the remaining characters after a match.

Explore padding strings in UnderscoreJS with the pad function to reach a target length using spaces or zeros, and learn left, right, and both padding directions and aliases.

Learn to use the natural cmp function as a comparator with array sort to achieve human-like string comparisons when numbers appear in strings.

Learn all the functions available in the underscore library, practice using underscore in your web development projects, and experiment with a new underscore function each day.