basics.js

console.log("dynamically typed, no need to mention type");
console.log("var can be redeclared and updated,let cannot be redeclared but updated and none for const");
console.log("heloo");
alert("hiii")
x = null;
console.log(typeof x);
y = undefined
typeof y;
console.log(x);
console.log(typeof y);
let name = "molly"
x = 5;
console.log(x)
var e = 9;
var e = 99;
let n = 99
n = 95;
const age = 44;
typeof age;
let a;
console.log(a);
console.log("not with const");

console.log("var is global while let and const are not");
console.log("7 primitives int. boolean str null bigint undifined symbol");
let t = Symbol("hiii")
let d = BigInt("123")
console.log(typeof t)
console.log("key value pair")
const student = {
 namee : "molly",
 age :78,
 hobby : "singing",
  pass: true
};
console.log(student)
student["namee"] = "divi"
console.log(student["namee"])
console.log("const obj key value can be changed")
//this is single line comment
/*multiline*/
console.log("a^b",5**6)
let num1 = 3;
let num2 = "3";
console.log(num1==num2)
//strict version
console.log(num1===num2)

let ages = 56;
if(ages<=18){
  console.log("cant vote");
}
else if(ages===22) console.log("can vote");
else console.log("can not vote");

let q = 75
q==55 ? console.log("cant diee"):q>76 ? console.log("live more"):console.log("leave");

for(var i = 1;i<=5;i++){
  console.log(i);
}
 console.log(i);
//will give error if i was let
console.log(5/4)//float
let str = "molly"
for(let i of str) console.log(i)//in gives index,of gives values
  let stu = {
   name:"DUSG",
   age:423,
   cgpa : 7.5

  
}
for(let keys in stu){
     console.log(stu[keys])
}
let string = "SINGLE CODE WILL ALSO WORK";
console.log(string.length)
//string is an object and are immutable

console.log(string)
let item = {
  price:10
}
console.log(item.price)
console.log(`the cost of item is ${10}`);
//template literal
//number is highlighted where string is not
//escape symbol like/n is  consided in len as 1
// all string methods does not cahnge original str
let g = "apna\ncollege"
console.log(g.length);

let neww = g.toUpperCase()
let namesss = "    heelooo my namee.   "
console.log(namesss.trim())//remove start and end space
console.log(namesss.slice(6,9)) //last index not inc.
console.log(namesss.concat(g))
g = g+namesss;//can be updated
console.log(g);
console.log(g.replace('h','w'));
console.log(g.slice(2))//till last index
let res = "hello" + 123
console.log(g.charAt(3))
//str[0] is not possible

let arr = [65,"hulk",true,7.9];
console.log(arr)
console.log(arr.length)//property not method
//arrays are mutable
arr.push("erg")
for(let i of arr) console.log(i)
  let del =arr.pop();
for(let i of arr) console.log(i)
  console.log(del)

console.log(arr.toString())//another array
let num = [1,2,3,4];
let v = num.concat(arr)
arr.unshift("erg");
  
for(let i of arr) console.log(i)
  let val = arr.shift();
console.log(val)
//slice is same as string
let ar = [1,2,3,4,5]
//splice changes original array
ar.splice(2,2,101,102)//del and replacefrom 2idx
ar.splice(2,0,103)//insert at 2
ar.splice(3,2) //del 2 elments from 3 idx
console.log(ar.splice(4)) // acts as slice and dletes it
console.log(ar)

function sum(w){
  w = w+5
  
  return w;
}

let w = 6;
console.log(sum(w));
console.log(w);

 const diff = (x,y) => {
  return x-y
}

console.log(diff(3,4))

const hellooo = (x,y) => {
    console.log(x+y);
} // arrow function

hellooo(5,7)

//methods are function that can only be used for certain data structure

//callback fn is passed as an argumnet in other  function
//for each methos can be used withh array map set nit with obj and string;
//x is each element of array
ar.forEach((x) => {
  console.log(x);
})//returns noting

ar.forEach(function call(val,idx,arr){
  console.log(val,idx,arr)
})




/*👉 A Higher Order Function is a function that:

✅ Takes another function as an argument
OR
like foreach
✅ Returns another function*/

//map return a new arr;

let arrayss = ar.map((val) => {
  return val*val;
})

console.log(arrayss)
//similary val idx and array is passed

//filter checks the consdition for every val in array and return new array of ele that satisfies


let r = ar.filter((val) => {
  return val%2==0;
})

//when values of array operated to single value like sum avg etc->reduce

let output = ar.reduce((prev,curr) => {
  return prev+curr;//return is stored in prev
})


console.log(output)

let ou = ar.reduce((prev,res)=>{
  return prev>res ? prev:res
})