JavaScript Basics Examples

const a=[{x:1},{x:2},{x:3}]; console.log(a.map(o=>o.x));

console.log("Hello, World!");

const a=5; const b=7; const sum=a+b; console.log(sum);

const base=10, height=5; const area=(base*height)/2; console.log(area);

let a=3,b=4; [a,b]=[b,a]; console.log(a,b);

const a=1,b=-3,c=2; const d=b*b-4*a*c; const r1=(-b+Math.sqrt(d))/(2*a); const r2=(-b-Math.sqrt(d))/(2*a); console.log(r1,r2);

const km=10; const miles=km*0.621371; console.log(miles);

const c=25; const f=(c*9/5)+32; console.log(f);

function rand(min,max){return Math.floor(Math.random()*(max-min+1))+min;} console.log(rand(1,100));

const n=0; console.log(n>0?"positive":n<0?"negative":"zero");

function isEven(n){return n%2===0;} console.log(isEven(7));

const a=5,b=17,c=9; console.log(Math.max(a,b,c));

function calc(a,b,op){switch(op){case "+":return a+b;case "-":return a-b;case "*":return a*b;case "/":return b? a/b: NaN; default:return NaN;}} console.log(calc(6,3,"*"));

const a=27,b=57; console.log(a%10===b%10);

function factors(n){const f=[]; for(let i=1;i<=n;i++){if(n%i===0)f.push(i);} return f;} console.log(factors(28));

const target=Math.floor(Math.random()*10)+1; const guess=7; console.log(guess===target?"Correct":"Try again: "+target);

const cards=[]; const suits=["H","D","C","S"], ranks=["A","2","3","4","5","6","7","8","9","10","J","Q","K"]; for(const s of suits){for(const r of ranks){cards.push(r+s);}} for(let i=cards.length-1;i>0;i--){const j=Math.floor(Math.random()*(i+1)); [cards[i],cards[j]]=[cards[j],cards[i]];} console.log(cards.slice(0,10));

const n=42; console.log(n.toString(2));

const ch="A"; console.log(ch.charCodeAt(0));

const s="banana apple cherry"; console.log(s.split(/\s+/).sort().join(" "));

function count(s,ch){let c=0; for(const x of s){if(x===ch)c++;} return c;} console.log(count("hello","l"));

const s="JavaScript"; console.log(s.startsWith("Java"), s.endsWith("ipt"));

const n=1234.56; console.log(n.toLocaleString("en-US",{style:"currency",currency:"USD"}));

console.log("JavaScript".startsWith("Java"));

function isLeapYear(y){return (y%4===0 && y%100!==0) || y%400===0;} console.log(isLeapYear(2024));

const a=[2,3]; a.unshift(1); console.log(a);

const v=null; console.log(v==null);

function greet(name="Guest"){console.log("Hello, "+name);} greet();

const A=new Set([1,2,3]), B=new Set([2,3,4]); const union=new Set([...A,...B]); const inter=new Set([...A].filter(x=>B.has(x))); const diff=new Set([...A].filter(x=>!B.has(x))); console.log(union,inter,diff);

function rand(min,max){return Math.floor(Math.random()*(max-min+1))+min;} console.log(rand(10,20));

console.log(window.location.href);

const fn=()=>{}; console.log(typeof fn==="function");

const PI=3.14159; console.log(PI);

const nums=Array.from({length:10},(_,i)=>i+1); const chars=Array.from({length:5},(_,i)=>String.fromCharCode(65+i)); console.log(nums,chars);

function add(){return [...arguments].reduce((a,b)=>a+b,0);} console.log(add(1,2,3));

class Stack{constructor(){this.a=[];} push(x){this.a.push(x);} pop(){return this.a.pop();} peek(){return this.a[this.a.length-1];}} const s=new Stack(); s.push(1); s.push(2); console.log(s.pop());

class Queue{constructor(){this.a=[];} enqueue(x){this.a.push(x);} dequeue(){return this.a.shift();} front(){return this.a[0];}} const q=new Queue(); q.enqueue(1); q.enqueue(2); console.log(q.dequeue());

const n=3.14; console.log(Number.isInteger(n)?"integer":"float");

function applyTwice(f,x){return f(f(x));} const inc=x=>x+1; console.log(applyTwice(inc,3));

const img=new Image(); img.onload=()=>console.log(img.width,img.height); img.src="https://via.placeholder.com/150";

const s=" a b \t c \n"; console.log(s.replace(/\s+/g,""));

console.log("log"); console.warn("warn"); console.error("error");