JavaScript test

var s="aaaabbbb";
console.log( s.match(/a*b/)+"" );  
console.log( s.match(/a*b*/)+"" );

var s="ab";
console.log( /a?b/.test(s) );  
console.log( /x?b/.test(s) );  
console.log( /x?b?/.test(s) );
console.log( /x?y?/.test(s) ); 

function intRoot1(n){
  return Number.isInteger(Math.sqrt(n));
}
function intRoot2(n){
  return Math.sqrt(n)%1==0;
}
function intRoot3(n){
  var x=Math.round(Math.sqrt(n));
  return x*x==n;
}

console.log(intRoot1(16))              
console.log(intRoot2(16))               
console.log(intRoot3(16))      

function removeOdd(arr){ 
  for (var i=0;i<arr.length;i++)
    if (arr[i]%2) arr.splice(i,1)
  return arr;
}
console.log(removeOdd([1,3,5,7,9]))  

var word="abcd";
var regstr=word[0]                             
          +word.slice(1,-1).replace(/./g,".")  
          +word.slice(-1);                    
var reg1=new RegExp("^"+regstr+"$");
console.log(reg1) 

var a=[1,2,3,4,5];
var b=a.filter(x=>x%2);
console.log(b);

function capIt(str){
  return str.split(/ /)
            .map(s=>s.replace(/^./,x=>x.toUpperCase()))
            .join(" ")
}
console.log( capIt("hello world!"))  
console.log( capIt("my name is John."))

const a = '10';
const b = 20;
const c = '30.5';

const result = Number(a) + b + Number.parseFloat(c);

console.log(result);

var str="aaaabbbb";
console.log( str.match(/a{0,0}b/)+"" );   
console.log( str.match(/a{0,1}b/)+"" );   
console.log( str.match(/a{0,2}b/)+"" );   
console.log( str.match(/a{0,100}b/)+"" );

var str="abcdef";
console.log( str.match(/./g) )   
console.log( str.match(/../g) ) 
console.log( str.match(/.../g) )

let str = "Hello, World!";
let result = str.substring(7, 12);
console.log(result);

var str="Hello beautiful World!";
console.log(str.slice(16,21))
console.log(str.substring(16,21))
console.log(str.slice(16,-1))

function decode(str){
  var chars=str.split("");
  for (var i=0;i<chars.length;i++) 
    chars[i]=String.fromCharCode(chars[i].charCodeAt()-1);
  return chars.join("");
}
function encode(str){
  var chars=str.split("");
  for (var i=0;i<chars.length;i++) 
    chars[i]=String.fromCharCode(chars[i].charCodeAt()+1);
  return chars.join("");
}
var s="abcde"
s=encode(s);
console.log("encode:",s)
s=decode(s);
console.log("decode:",s)

function displayArguments() {
  console.log(arguments.length);
  console.log(arguments[0]);
  console.log(arguments[2]);
}

displayArguments('Hello', 'World', 'JavaScript', 'Quiz');

var str="My name is John";
var words=str.split("");
console.log(words);

function trickyFunction() {
  let a = 5;
  let b = '5';
  let c = 5;

  if (a == b && b === c) {
    console.log('Condition 1');
  } else if (a === c || b == c) {
    console.log('Condition 2');
  } else {
    console.log('Condition 3');
  }
}

trickyFunction();

var obj = { a: 10, b: 20 };

with (obj) {
  var result = a + b;
}

console.log(result);

const myObject = {
  a: 1,
  b: 2,
  c: 3,
  [Symbol.iterator]: function* () {
    for (let key of Object.keys(this)) {
      yield this[key];
    }
  }
};

const iter = myObject[Symbol.iterator]();
console.log(iter.next().value);
console.log(iter.next().value);
console.log(iter.next().value);

function* customGenerator() {
    yield 'Hello';
    yield 'World';
    return 'Done';
}

const gen = customGenerator();
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);

const mySet = new Set();
mySet.add(10);
mySet.add(20);
mySet.add(10);
mySet.add(30);

console.log(mySet.size);