// Returns a random number(float) between min (inclusive) and max (exclusive) constgetRandomNumber=(min,max)=>Math.random()*(max-min)+min;getRandomNumber(2,10)// Returns a random number(int) between min (inclusive) and max (inclusive)constgetRandomNumberInclusive=(min,max)=>{min=Math.ceil(min);max=Math.floor(max);returnMath.floor(Math.random()*(max-min+1))+min;}getRandomNumberInclusive(2,10);

constfirstArr=[5,2,1];constsecondArr=[1,2,3,4,5];constdiff=[ ...secondArr.filter(x=>!firstArr.includes(x)), ...firstArr.filter(x=>!secondArr.includes(x))];console.log('diff',diff)//[3,4]functionarrayDiff(a,b){return[ ...a.filter(x=>b.indexOf(x)===-1), ...b.filter(x=>a.indexOf(x)===-1)]}console.log('arrayDiff',arrayDiff(firstArr,secondArr))//[3,4]constdifference=(a,b)=>{constsetA=newSet(a);constsetB=newSet(b);return[ ...a.filter(x=>!setB.has(x)), ...b.filter(x=>!setA.has(x))]};difference(firstArr,secondArr);//[3,4]console.log('difference',difference(firstArr,secondArr))

constmyVar=null;constmySecondVar=1;console.log(Boolean(myVar))// falseconsole.log(!!myVar)// falseconsole.log(Boolean(mySecondVar))// trueconsole.log(!!mySecondVar)// true

letaliens='';for(leti=0;i<6;i++){aliens+='👽'}//👽👽👽👽👽👽Array(6).join('👽')//👽👽👽👽👽👽'👽'.repeat(6)//👽👽👽👽👽👽

//The performance.now() method returns a DOMHighResTimeStamp, measured in milliseconds.//performance.now() is relative to page load and more precise in orders of magnitude. //Use cases include benchmarking and other cases where a high-resolution time is required //such as media (gaming, audio, video, //etc.)varstartTime=performance.now();doSomething();constendTime=performance.now();console.log("this doSomething took "+(endTime-startTime)+" milliseconds.");

//Mutating wayconstmuatatedArray=['a','b','c','d','e'];muatatedArray.splice(2,1)console.log(muatatedArray)//['a','b','d','e']//Non-mutating wayconstnonMuatatedArray=['a','b','c','d','e'];constnewArray=nonMuatatedArray.filter((item,index)=>!(index===2));console.log(newArray)//['a','b','d','e']

constmyArray=[2,3,[4,5],[7,7,[8,9,[1,1]]]];myArray.flat()// [2, 3, 4, 5 ,7,7, [8, 9, [1, 1]]]myArray.flat(1)// [2, 3, 4, 5 ,7,7, [8, 9, [1, 1]]]myArray.flat(2)// [2, 3, 4, 5 ,7,7, 8, 9, [1, 1]]//if you dont know the depth of the array you can use infinitymyArray.flat(infinity)// [2, 3, 4, 5 ,7,7, 8, 9, 1, 1];

constnumbers=[1,1,3,2,5,3,4,7,7,7,8];//Ex1constunieqNumbers=numbers.filter((v,i,a)=>a.indexOf(v)===i)console.log(unieqNumbers)//[1,3,2,5,4,7,8]//Ex2constunieqNumbers2=Array.from(newSet(numbers))console.log(unieqNumbers2)//[1,3,2,5,4,7,8]//Ex3constunieqNumbers3=[...newSet(numbers)]console.log(unieqNumbers3)//[1,3,2,5,4,7,8]//EX4 lodashconstunieqNumbers4=_.uniq(numbers)console.log(unieqNumbers4)//[1,3,2,5,4,7,8]

functioncopyToClipboard(){constcopyText=document.getElementById("myInput");copyText.select();document.execCommand("copy");}//new APIfunctioncopyToClipboard(){navigator.clipboard.writeText(document.querySelector('#myInput').value)}

constuser={id: 459,name: 'JS snippets',age:29,education:{degree: 'Masters'}}const{education : { degree }}=user;console.log(degree)//Masters

//The URLSearchParams interface defines utility methods to work with the query string of a URL.consturlParams=newURLSearchParams("?post=1234&action=edit");console.log(urlParams.has('post'));// trueconsole.log(urlParams.get('action'));// "edit"console.log(urlParams.getAll('action'));// ["edit"]console.log(urlParams.toString());// "?post=1234&action=edit"console.log(urlParams.append('active','1'));// "?post=1234&action=edit&active=1"

constmyFruits=['Apple','Orange','Mango','Banana','Apple','Apple','Mango']//first optionconstcountMyFruits=myFruits.reduce((countFruits,fruit)=>{countFruits[fruit]=(countFruits[fruit]||0)+1;returncountFruits},{})console.log(countMyFruits)// { Apple:3, Banana:1, Mango:2, Orange:1 }//seconf optionconstfruitsCounter={};for(constfruitofmyFruits){fruitsCounter[fruit]=fruitsCounter[fruit] ? fruitsCounter[fruit]+1 :1;}console.log(fruitsCounter)// { Apple:3, Banana:1, Mango:2, Orange:1 }

//There are cases where you want the destructured variable to have a different name than the property nameconstobj={name: "JSsnippets"};// Grabs obj.name as { pageName }const{name: pageName}=obj;//log our aliasconsole.log(pageName)// JSsnippets

Object.is('foo','foo');// trueObject.is(null,null);// trueObject.is(Nan,Nan);// true 😱constfoo={a: 1};constbar={a: 1};Object.is(foo,foo);// trueObject.is(foo,bar);// false

constobj={name: "JSsnippets",age:29,address:{street : 'JS'}};constfrozenObject=Object.freeze(obj);frozenObject.name='weLoveJS';// Uncaught TypeError//Although, we still can change a property’s value if it’s an object:frozenObject.address.street='React';// no error, new value is setdeletefrozenObject.name// Cannot delete property 'name' of #<Object>//We can check if an object is frozen by usingObject.isFrozen(obj)//true

constobj={name: "JSsnippets",age:29,};//Object.entries() method is used to return an array consisting of enumerable property //[key, value] pairs of the object which are passed as the parameter.for(let[key,value]ofObject.entries(obj)){console.log(`${key}: ${value}`)}//expected output:// "name: Jssnippets"// "age: 29"// order is not guaranteed

window.oncontextmenu=()=>{console.log('right click');returnfalse// cancel default menu}//orwindow.addEventListener('contextmenu',()=>{console.log('right click');returnfalse// cancel default menu},false)

//Without async or defer, browser will run your script immediately, before rendering the elements that's below your script tag.<scriptsrc="myscript.js"></script>//With async (asynchronous), browser will continue to load the HTML page and render it while the browser load and execute the script at the same time.//Async is more useful when you really don't care when the script loads and nothing else that is user dependent depends upon that script loading.(for scripts likes Google analytics)<scriptasyncsrc="myscript.js"></script> //With defer, browser will run your script when the page finished parsing. (not necessary finishing downloading all image files. <scriptdefersrc="myscript.js"></script>

// an equality check against nullary values (e.g. null or undefined). Whenever the expression to the left of the ?? operator evaluates to either //undefined or null, the value defined to the right will be returned.constfoo=undefined??'default string';console.log(foo);// expected output: "default string"constage=0??30;console.log(age);// expected output: "0"

constcar={}constcarColor=car.name.colorconsole.log(carColor);// error- "Uncaught TypeError: Cannot read property 'carColor' of undefined //In JavaScript, you can first check if an object exists, and then try to get one of its properties, like this:constcarColor=car&&car.name&&car.name.color;console.log(carColor);//undefined- no error//Now this new optional chaining operator will let us be even more fancy:constnewCarColor=car?.name?.color;console.log(newCarColor)//undefined- no error//You can use this syntax today using @babel/plugin-proposal-optional-chaining

AccessingtheglobalpropertyinJavaScripthasalwaysposedsomedifficulty.Thisisbecausedifferentplatformshavedifferentwaystoaccessit.Client-sideJavaScriptuseswindoworselfNode.jsusesglobalWebworkersuseselfTheglobalThispropertyprovidesastandardwayofaccessingtheglobal'this'valueacrossenvironments.youcanaccesstheglobalobjectinaconsistentmannerwithouthavingtoknowwhichenvironmentthecodeisbeingrunin.console.log(globalThis)//get the global this depends on your environment

constuser={id: 459,name: 'JS snippets',age:29,education:{degree: 'Masters'}}JSON.stringify(user,[name,age],2)/*returns{ "name": "JS snippets", "age": 29}*/

constel=document.getElementById("btn");functionmyClickHandler(){console.log('this click will only fire once')}el.addEventListener('click',myClickHandler,{once: true,});

constspan=document.querySelector("span");letclasses=span.classList;span.addEventListener("click",function(){letresult=classes.toggle("active");if(result){console.log("active class was added");}else{console.log("active class was removed");}});

functionisJson(str){try{JSON.parse(str);}catch(e){//the json is not okreturnfalse;}//the json is okreturntrue;}

//getBoundingClientRect provides you with important pieces of data about an//HTML element’s size and positioning.constbodyBounderies=document.body.getBoundingClientRect();// => {// top: Number,// left: Number,// right: Number,// bottom: Number,// x: Number,// y: Number,// width: Number,// height: Number,// }

constimage=document.querySelector('.animate-me');observer=newIntersectionObserver((entries)=>{const[myImg]=entries;if(myImg.intersectionRatio>0){myImg.target.classList.add('fancy');}else{myImg.target.classList.remove('fancy');}});observer.observe(image);

constfoo=document.getElementById("foo");constobserver=newResizeObserver((entries)=>{for(letentryofentries){constcr=entry.contentRect;console.log=`Size: ${cr.width}px X ${cr.height}px`;}});observer.observe(foo);

constvideo=document.getElementById("my-video");constonVisibilitychange=()=>{returndocument.hidden ? video.pause() : video.play();}document.addEventListener("visibilitychange",onVisibilitychange)

classStudents{ #name;constructor(){this.#name ="JS snippets";} #privateMethod(){return'Come and learn Js with us';}getPrivateMessage(){returnthis.#privateMethod();}}constinstance=newSomething();console.log(instance.name);//=> undefinedconsole.log(instance.privateMethod);//=> undefinedconsole.log(instance.getPrivateMessage());//=> Come and learn Js with us

constpasteBox=document.getElementById("paste-no-event");pasteBox.onpaste=(e)=>{e.preventDefault();returnfalse;};

void0;//returns undefinedvoid(0);//returns undefinedvoid{};//returns undefinedvoid "JSsnippets; //returns undefined void(0);//returns undefinedvoid(2=='2');//returns undefinedvoidanyfunction();//returns undefined

conststr='this is a JSsnippets example';constupdatedStr=str.replace('example','snippet');// 'this is a JSsnippets snippet'Thetrickypartisthatreplacemethodreplacesonlytheveryfirstmatchofthesubstringwehave passed: conststr='this is a JSsnippets example and examples are great';constupdatedStr=str.replace('example','snippet');//'this is a JSsnippets snippet and examples are great'Inordertogothroughthis,weneedtouseaglobalregexpinstead: conststr='this is a JSsnippets example and examples are great';constupdatedStr=str.replace(/example/g,'snippet');//'this is a JSsnippets snippet and snippets are greatr'butnowwehavenewfriendintown,replaceAllconststr='this is a JSsnippets example and examples are great';constupdatedStr=str.replaceAll('example','snippet');//'this is a JSsnippets snippet and snippets are greatr'

constisRequired=()=>{thrownewError('This is a mandatory parameter.');}constgetPage=(pageName='Jssnippets',url=isRequired())=>{return`${pageName}${url}`;}console.log(getPage());//In the above code, url will be undefined and that will try to set the default value for it which is the isRequired() function. It will throw an error as,//Uncaught error: This is a mandatory parameter.//at isRequired

<inputtype="number"id="JSsnippets"onkeyup="checkMyType(event)"/>functioncheckMyType(event){console.log(typeofevent.target.value)// stringconsole.log(typeofevent.target.valueAsNumber)// number}

constarr=["a","b","c","d","e"]constreduceArray=arr.reduce((acc,current)=>{returnacc+current},"")//return abcdeconstreduceRightArray=arr.reduceRight((acc,current)=>{returnacc+current},"")//return edcba

//HTML<buttonid="download">Download</button><buttonid="abort">Abort</button>//JSletcontroller;document.querySelector('#download').addEventListener('click',()=>{controller=newAbortController();constsignal=controller.signal;fetch('https://cdn.plyr.io/static/demo/View_From_A_Blue_Moon_Trailer-576p.mp4',{signal}).then(()=>console.log('done'));});document.querySelector('#abort').addEventListener('click',function(){controller.abort();});

conststate=[{userId: 1,name: "JSSnippets",isOwner: false,},{userId: 2,name: "React",isOwner: false,},{userId: 3,name: "Vue",isOwner: false,},{userId: 4,name: "Angular",isOwner: false,},];constnewState=state.map((obj)=>obj.name==="JSSnippets" ? { ...obj,isOwner: true} : obj);

// Three quick steps to shuffle an array in Javascript: Map to a random number, sort on that and map the object back! shuffleArray=anArray=>anArray.map(a=>[Math.random(),a]).sort((a,b)=>a[0]-b[0]).map(a=>a[1]);console.log('Shuffled array',shuffleArray([1,2,3,4,5,6,7,8,9,10]))// Returns shuffled array