Computers are extremely good at following directions. You can think of a computer as a very efficient and experienced waiter who follows your order exactly. But the real "driving force" behind this efficiency is the Conditional Statement.
​Whether it's checking if a number is even or deciding if you've won a game, it all works on this structure. Conditional statements are fundamental concepts in the world of programming that allow code to execute only when specific conditions are met.
​Imagine a real-world scenario: If it's raining outside, stay inside; else, go out. In Python, we have three primary ways to handle these choices.

​1. The if Statement: The Security Guard
​Think of a school security guard on duty at night. He has one specific instruction:
​"Check if any light in the building is on. If it is, turn it off."
​If the light is already off, he simply goes back to the gate. He doesn't have a "Plan B"; he only acts if the specific condition (Light is ON) is true.
​In Technical Terms: The if statement executes a block of code only if the condition is True. If it's False, Python ignores the code entirely.

#The Security Guard Logic
light_is_on = True

if light_is_on:
    print("Action: Turn the light off.") 

2. The if-else Statement: The Cricket Toss
​Consider the toss at the start of a cricket match. This is a "two-way" choice:
​If it's Heads → Team A will bat first.
​Else (it must be Tails) → Team A will bowl first.
​In technical terms, if the condition is true, the first statement executes; if it is false, the else statement executes.

#The Cricket Toss Logic
toss_result = "Tails"

if toss_result == "Heads":
    print("Team A will Bat first.")
else:
    print("Team A will Bowl first.")

3. The if-elif-else Ladder: The Restaurant Menu
​Imagine you are at a restaurant with a limited amount of cash in your pocket. You have to make a choice based on your budget:
​If you have Rs. 500 → Eat Chicken Biryani.
​Elif (Else-if) you have Rs. 300 → Eat Chicken Pulao.
​Else (less than Rs. 300) → Just get a Milkshake.
​In Technical Terms: This statement chooses between multiple conditions. As soon as one is found True, it executes that specific block and skips the rest.

# The Budget Logic
cash_in_hand = 450

if cash_in_hand >= 500:
    print("Ordering: Chicken Biryani")
elif cash_in_hand >= 300:
    print("Ordering: Chicken Pulao")
else:
    print("Ordering: Chilled Milkshake")

🔢 Mathematical Application: The Even-Odd Logic
​To see how this works in a mathematical context, let’s look at how a computer identifies even and odd numbers. We use the Modulo Operator (%), which gives us the remainder of a division.
​A) The Simple Check (If)
​

Checking for a single specific condition.
n = 10
if n % 2 == 0:
    print("The number is Even")

B) The Two-Way Categorization (If-Else)
​

Handling both possibilities.
n = 7
if n % 2 == 0:
    print("Even")
else:
    print("Odd")

C) The Multi-Case Logic (If-Elif-Else)

​Checking for Positive, Negative, or Zero.n = 0
if n > 0:
    print("Positive Number")
elif n < 0:

Conclusion
​Conditional statements are the "brain" of your code. By mastering these three structures, you can build programs that react to the world just like we do.

Read more of this story at Slashdot.

Deprecated APIs removed

These functions have been deprecated for several versions. It’s time to remove them now that we’ve reached a major release. These functions were either always meant to be internal or ones that now have native equivalents in all supported browsers. The removed functions include:

jQuery.isArray, jQuery.parseJSON, jQuery.trim, jQuery.type, jQuery.now, jQuery.isNumeric, jQuery.isFunction, jQuery.isWindow, jQuery.camelCase, jQuery.nodeName, jQuery.cssNumber, jQuery.cssProps, and jQuery.fx.interval.

Use native equivalents like Array.isArray(), JSON.parse(), String.prototype.trim(), and Date.now() instead.

The removal of deprecated APIs combined with the removal of code supporting old IE the result is a size reduction over 3k bytes gzipped.

Internal-only methods removed from jQuery prototype

The jQuery prototype has long had Array methods that did not behave like any other jQuery methods and were always meant for internal-use only. These methods are push, sort, and splice. They have now been removed from the jQuery prototype. If you were using these methods, $elems.push( elem ) can be replaced with [].push.call( $elems, elem ).

Focus event order now follows W3C spec

For a long time, browsers did not agree on the order of focus and blur events, which includes focusin, focusout, focus, and blur. Finally, the latest versions of all browsers that jQuery 4.0 supports have converged on a common event order. Unfortunately, it differs from the consistent order that jQuery had chosen years ago, which makes this a breaking change. At least everyone is on the same page now!

Starting with jQuery 4.0, we no longer override native behavior. This means that all browsers except IE will follow the current W3C specification, which is:

1. blur
2. focusout
3. focus
4. focusin

jQuery’s order in previous versions was: focusout, blur, focusin, focus. Ironically, the only browser to ever follow the old W3C spec (before it was updated in 2023) was Internet Explorer.

Updated slim build

The slim build has gotten even smaller in jQuery 4.0.0 with the removal of Deferreds and Callbacks (now around 19.5k bytes gzipped!). Deferreds have long-supported the Promises A+ standard, so native Promises can be used instead in most cases and they are available in all of jQuery’s supported browsers except IE11. Deferreds do have some extra features that native Promises do not support, but most usage can be migrated to Promise methods. If you need to support IE11, it’s best to use the main build or add a polyfill for native Promises.

Download

You can get the files from the jQuery CDN, or link to them directly:

https://code.jquery.com/jquery-4.0.0.js

https://code.jquery.com/jquery-4.0.0.min.js

You can also get this release from npm:

npm install jquery@4.0.0

Slim build

Sometimes you don’t need ajax, or you prefer to use one of the many standalone libraries that focus on ajax requests. And often it is simpler to use a combination of CSS and class manipulation for web animations. Finally, all of jQuery’s supported browsers (except for IE11) now have support for native Promises across the board, so Deferreds and Callbacks are no longer needed in most cases. Along with the regular version of jQuery that includes everything, we’ve released a “slim” version that excludes these modules. The size of jQuery is very rarely a load performance concern these days, but the slim build is about 8k gzipped bytes smaller than the regular version. These files are also available in the npm package and on the CDN:

https://code.jquery.com/jquery-4.0.0.slim.js

https://code.jquery.com/jquery-4.0.0.slim.min.js

These updates are already available as the current versions on npm and Bower. Information on all the ways to get jQuery is available at https://jquery.com/download/. Public CDNs receive their copies today, please give them a few days to post the files. If you’re anxious to get a quick start, use the files on our CDN until they have a chance to update.

Thanks

Thank you to all of you who participated in this release by submitting patches, reporting bugs, or testing, including Alex, Ahmed S. El-Afifi, fecore1, Dallas Fraser, Richard Gibson, Michał Gołębiowski-Owczarek, Pierre Grimaud, Gabriela Gutierrez, Jonathan, Necmettin Karakaya, Anders Kaseorg, Wonseop Kim, Simon Legner, Shashanka Nataraj, Pat O’Callaghan, Christian Oliff, Dimitri Papadopoulos Orfanos, Wonhyoung Park, Bruno PIERRE, Baoshuo Ren, Beatriz Rezener, Sean Robinson, Ed Sanders, Timo Tijhof, Tom, Christian Wenz, ygj6 and the whole jQuery team.

Happy 20th Birthday jQuery!

Lots of wonderful people have contributed to jQuery and its associated projects in the past 20 years and many of us met up for a reunion in Dallas. John Resig even joined over Zoom. This release was posted while we were all together.

Changelog

Full changelog: 4.0.0

Ajax

• Don't treat array data as binary (992a1911)
• Allow processData: true even for binary data (ce264e07)
• Support binary data (including FormData) (a7ed9a7b)
• Support headers for script transport even when cross-domain (#5142, 6d136443)
• Support null as success functions in jQuery.get (#4989, 74978b7e)
• Don't auto-execute scripts unless dataType provided (#4822, 025da4dd)
• Make responseJSON work for erroneous same-domain JSONP requests (68b4ec59)
• Execute JSONP error script responses (#4771, a1e619b0)
• Avoid CSP errors in the script transport for async requests (#3969, 07a8e4a1)
• Drop the json to jsonp auto-promotion logic (#1799, #3376, e7b3bc48)
• Overwrite s.contentType with content-type header value, if any (#4119, 7fb90a6b)
• Deprecate AJAX event aliases, inline event/alias into deprecated (23d53928)
• Do not execute scripts for unsuccessful HTTP responses (#4250, 50871a5a)
• Simplify jQuery.ajaxSettings.xhr (#1967, abdc89ac)

Attributes

• Make .attr( name, false ) remove for all non-ARIA attrs (#5388, 063831b6)
• Shave off a couple of bytes (b40a4807)
• Don't stringify attributes in the setter (#4948, 4250b628)
• Drop the toggleClass(boolean|undefined) signature (#3388, a4421101)
• Refactor val(): don't strip carriage return, isolate IE workarounds (ff281991)
• Don't set the type attr hook at all outside of IE (9e66fe9a)

CSS

• Fix dimensions of table <col> elements (#5628, eca2a564)
• Drop the cache in finalPropName (640d5825)
• Tests: Fix tests & support tests under CSS Zoom (#5489, 071f6dba)
• Fix reliableTrDimensions support test for initially hidden iframes (b1e66a5f)
• Selector: Align with 3.x, remove the outer selector.js wrapper (53cf7244)
• Make the reliableTrDimensions support test work with Bootstrap CSS (#5270, 65b85031)
• Make offsetHeight( true ), etc. include negative margins (#3982, bce13b72)
• Return undefined for whitespace-only CSS variable values (#5120) (7eb00196)
• Don’t trim whitespace of undefined custom property (#5105, ed306c02)
• Skip falsy values in addClass( array ), compress code (#4998, a338b407)
• Justify use of rtrim on CSS property values (655c0ed5)
• Trim whitespace surrounding CSS Custom Properties values (#4926, efadfe99)
• Include show, hide & toggle methods in the jQuery slim build (297d18dd)
• Remove the opacity CSS hook (865469f5)
• Workaround buggy getComputedStyle on table rows in IE/Edge (#4490, 26415e08)
• Don't automatically add "px" to properties with a few exceptions (#2795, 00a9c2e5)

Core

• Remove obsolete workarounds, update support comments (e2fe97b7)
• Switch $.parseHTML from document.implementation to DOMParser (0e123509)
• Fix the exports setup to make bundlers work with ESM & CommonJS (#5416, 60f11b58)
• Add more info about named exports (5f869590)
• Simplify code post browser support reduction (93ca49e6)
• Move the factory to separate exports (46f6e3da)
• Use named exports in src/ (#5262, f75daab0)
• Fix regression in jQuery.text() on HTMLDocument objects (#5264, a75d6b52)
• Selector: Move jQuery.contains from the selector to the core module (024d8719)
• Drop the root parameter of jQuery.fn.init (d2436df3)
• Don't rely on splice being present on input (9c6f64c7)
• Manipulation: Add basic TrustedHTML support (#4409, de5398a6)
• Report browser errors in parseXML (#4784, 89697325)
• Make jQuery.isXMLDoc accept falsy input (#4782, fd421097)
• Drop support for Edge Legacy (i.e. non-Chromium Microsoft Edge) (#4568, e35fb62d)
• Fire iframe script in its context, add doc param in globalEval (#4518, 4592595b)
• Exclude callbacks & deferred modules in the slim build as well (fbc44f52)
• Migrate from AMD to ES modules (d0ce00cd)
• Use Array.prototype.flat where supported (#4320, 9df4f1de)
• Remove private copies of push, sort & splice from the jQuery prototype (b59107f5)
• Implement .even() & .odd() to replace POS :even & :odd (78420d42)
• Deprecate jQuery.trim (#4363, 5ea59460)
• Remove IE-specific support tests, rely on document.documentMode (#4386, 3527a384)
• Drop support for IE <11, iOS <11, Firefox <65, Android Browser & PhantomJS (#3950, #4299, cf84696f)
• Remove deprecated jQuery APIs (#4056, 58f0c00b)

Data

• Refactor to reduce size (805cdb43)
• Event:Manipulation: Prevent collisions with Object.prototype (#3256, 9d76c0b1)
• Separate data & css/effects camelCase implementations (#3355, 8fae2120)

Deferred

• Rename getStackHook to getErrorHook (#5201, 258ca1ec)
• Respect source maps in jQuery.Deferred.exceptionHook (#3179, 0b9c5037)
• Rename master to primary (a32cf632)

Deprecated

• Define .hover() using non-deprecated methods (fd6ffc5e)
• Remove jQuery.trim (0b676ae1)
• Fix AMD parameter order (f810080e)

Dimensions

• Add offset prop fallback to FF for unreliable TR dimensions (#4529, 3bbbc111)

Docs

• Fix some minor issues in comments (e4d4dd81)
• update herodevs link in README (#5695, 093e63f9)
• Align CONTRIBUTING.md with 3.x-stable (d9281061)
• Update CONTRIBUTING.md (4ef25b0d)
• add version support section to README (cbc2bc1f)
• Update remaining HTTP URLs to HTTPS (7cdd8374)
• Fix module links in the package README (ace646f6)
• update watch task in CONTRIBUTING.md (77d6ad71)
• Fix typos found by codespell (620870a1)
• remove stale gitter badge from readme (67cb1af7)
• Remove the "Grunt build" section from the PR template (988a5684)
• Remove stale badge from README (bcd9c2bc)
• Update the README of the published package (edccabf1)
• Remove git.io from a GitHub Actions comment (016872ff)
• Update webpack website in README (01819bc3)
• add link to patchwelcome and help wanted issues (924b7ce8)
• add link to preview the new CLAs (683ceb8f)
• Fix incorrect trac-NUMBER references (eb9ceb2f)
• remove expired links from old jquery source (#4997) (ed066ac7)
• Remove links to Web Archive from source (#4981, e24f2dcf)
• Replace #NUMBER Trac issue references with trac-NUMBER (5d5ea015)
• Update the URL to the latest jQuery build in CONTRIBUTING.md (9bdb16cd)
• Remove the CLA checkbox in the pull request template (e1248931)
• update irc to Libera and fix LAMP dead link (175db73e)
• Update Frequently Reported Issues in the GitHub issue template (7a6fae6a)
• Change JS Foundation mentions to OpenJS Foundation (11611967)
• add SECURITY.md, show security email address (2ffe54ca)
• Fix typos (1a7332ce)
• Update the link to the jsdom repository (a62309e0)
• Use https for hyperlinks in README (73415da2)
• Remove a mention of the event/alias.js module from README (3edfa1bc)
• Update links to EdgeHTML issues to go through Web Archive (1dad1185)
• direct users to GitHub docs for cloning the repo (f1c16de2)
• Change OS X to macOS in README (5a3e0664)
• Update most URLs to HTTPS (f09d9210)
• Convert link to Homebrew from HTTP to HTTPS (e0022f23)

Effect

• Fix a unnecessary conditional statement in .stop() (#4374, 110802c7)

Effects

• Remove jQuery.fx.interval (6c2c7362)

Event

• Use .preventDefault() in beforeunload (7c123dec)
• Increase robustness of an inner native event in leverageNative (#5459, 527fb3dc)
• Avoid collisions between jQuery.event.special & Object.prototype (bcaeb000)
• Simplify the check for saved data in leverageNative (dfe212d5)
• Make trigger(focus/blur/click) work with native handlers (#5015, 6ad3651d)
• Simulate focus/blur in IE via focusin/focusout (#4856, #4859, #4950, ce60d318)
• Don't break focus triggering after .on(focus).off(focus) (#4867, e539bac7)
• Make focus re-triggering not focus the original element back (#4382, dbcffb39)
• Don't crash if an element is removed on blur (#4417, 5c2d0870)
• Remove the event.which shim (#3235, 1a5fff4c)
• remove jQuery.event.global (18db8717)
• Only attach events to objects that accept data – for real (#4397, d5c505e3)
• Stop shimming focusin & focusout events (#4300, 8a741376)
• Prevent leverageNative from registering duplicate dummy handlers (eb6c0a7c)
• Fix handling of multiple async focus events (#4350, ddfa8376)

Manipulation

• Make jQuery.cleanData not skip elements during cleanup (#5214, 3cad5c43)
• Generalize a test to support IE (88690ebf)
• Support $el.html(selfRemovingScript) (#5378) (#5377, 937923d9)
• Extract domManip to a separate file (ee6e8740)
• Don't remove HTML comments from scripts (#4904, 2f8f39e4)
• Respect script crossorigin attribute in DOM manipulation (#4542, 15ae3614)
• Avoid concatenating strings in buildFragment (9c98e4e8)
• Make jQuery.htmlPrefilter an identity function (90fed4b4)
• Selector: Use the nodeName util where possible to save size (4504fc3d)

Offset

• Increase search depth when finding the 'real' offset parent (556eaf4a)

Release

• 4.0.0 (4f2fae08)
• remove dist files from main branch (c838cfb5)
• 4.0.0-rc.2 (97525193)
• Update AUTHORS.txt (c128d5d8)
• Fix release issues uncovered during the 4.0.0-rc.1 release (a5b0c431)
• remove dist files from main branch (9d06c6dd)
• 4.0.0-rc.1 (586182f3)
• Run npm publish in the post-release phase (ff1f0eaa)
• Only run browserless tests during the release (fb5ab0f5)
• Temporarily disable running tests on release (3f79644b)
• publish tmp/release/dist folder when releasing (#5658, a865212d)
• correct build date in verification; other improvements (53ad94f3)
• remove dist files from main branch (be048a02)
• 4.0.0-beta.2 (51fffe9f)
• ensure builds have the proper version (3e612aee)
• set preReleaseBase in config file (1fa8df5d)
• fix running pre/post release scripts in windows (5518b2da)
• update AUTHORS.txt (862e7a18)
• migrate release process to release-it (jquery/jquery-release#114, 2646a8b0)
• add factory files to release distribution (#5411, 1a324b07)
• use buildDefaultFiles directly and pass version (b507c864)
• copy dist-module folder as well (63767650)
• only published versioned files to cdn (3a0ca684)
• remove scripts and dev deps from dist package.json (7eac932d)
• update build command in Release.generateArtifacts (3b963a21)
• add support for md5 sums in windows (f088c366)
• remove the need to install grunt globally (b2bbaa36)
• upgrade release dependencies (967af732)
• Remove an unused chalk dependency (bfb6897c)
• Use an in-repository dist README fixture (358b769a)
• Update AUTHORS.txt (1b74660f)
• update AUTHORS.txt (cf9fe0f6)

Selector

• Remove the workaround for :has; test both on iPhone & iPad (65e35450)
• Properly deprecate jQuery.expr[ ":" ]/jQuery.expr.filters (329661fd)
• Make selector.js module depend on attributes/attr.js (#5379, e06ff088)
• Eliminate selector.js depenencies from various modules (e8b7db4b)
• Re-expose jQuery.find.{tokenize,select,compile,setDocument} (#5259, 338de359)
• Stop relying on CSS.supports( "selector(…)" ) (#5194, 68aa2ef7)
• Backport jQuery selection context logic to selector-native (#5185, 2e644e84)
• Make selector lists work with qSA again (#5177, 09d988b7)
• Implement the uniqueSort chainable method (#5166, 5266f23c)
• Re-introduce selector-native.js (4c1171f2)
• Manipulation: Fix DOM manip within template contents (#5147, 3299236c)
• Drop support for legacy pseudos, test custom pseudos (8c7da22c)
• Use jQuery :has if CSS.supports(selector(...)) non-compliant (#5098, d153c375)
• Remove the "a:enabled" workaround for Chrome <=77 (c1ee33ad)
• Make empty attribute selectors work in IE again (#4435, 05184cc4)
• Use shallow document comparisons in uniqueSort (#4441, 15750b0a)
• Add a test for throwing on post-comma invalid selectors (6eee5f7f)
• Make selectors with leading combinators use qSA again (ed66d5a2)
• Use shallow document comparisons to avoid IE/Edge crashes (#4441, aa6344ba)
• reduce size, simplify setDocument (29a9544a)
• Leverage the :scope pseudo-class where possible (#4453, df6a7f7f)
• Bring back querySelectorAll shortcut usage (cef4b731)
• Inline Sizzle into the selector module (47835965)
• Port Sizzle tests to jQuery (79b74e04)

Support

• ensure display is set to block for the support div (#4832, 09f25436)

Traversing

• Fix contents() on <object>s with children in IE (ccbd6b93)
• Fix contents() on <object>s with children (#4384, 4d865d96)