JAVASCRIPT

JS FUNCTIONS //BASIC FUNCTION function   add ( a , b ){      console . log ( a + b ) } add ( 4 , 5 ) //Anonymous Func var   add  =  function  ( a , b ){      console . log ( a + b ) } var   ans  =  add ( 5 , 5 ) //IIFE ( function  ( a , b ){      console . log ( a + b ) })( 4 , 5 ) //ARROW FUNCTION var   add  =  ( a , b )  =>      console . log ( a + b ); add ( 7 , 5 ) PARAMETER COUNT vs ARGUMENT COUNT function   add ( a , b , c ) {      console . log ( a + b + c ) } add ( 1 , 2 , 3 )   //6 add ( 1 , 2 )     //NaN add ( 1 , 2 , 3 , 4 )  //6 DEFAULT PARAMETER function   add ( a = 10 , b , c ) {      console . log ( a + b + c ) } add ( 2 , 3 )  //NaN    

  DATA COMPARISON   = = = = =   // Strict Comparison   ! =   >=   <=                               NUMBER & STRING   10   = = “10”     // TRUE   10 = = = “10”   // FALSE   “2”>”12” // TRUE   Because 2 is greater than 1.In string comparison it will check index by index 12>”2” // True   ARRAY & OBJECT var arr1   = [1,2,3,4,5] var arr2   = [1,2,3,4,5] JSON.stringify(arr1)===JSON.stringify(arr2) // TRUE CASE 1 var obj1 = {‘name’:’happy’, ’place’ :’youtube’}   var obj2 = {‘name’:’happy’, ’place’ :’youtube’}   JSON.stringify(obj1)===JSON.stringify(obj2) //TRUE CASE 2 var obj1 = {‘name’:’happy’, ’place’ :’youtube’}   var obj2 = {’place’ :’youtube’, ‘name’:’happy’ }       ...

  DATA TYPE CONVERSION   NUMBER TO STRING var   a = 10 String(a)   STRING TO NUMBER var   a = ‘10’ Number(a); parseInt(a); parseInt(“10.4”) or parseInt(“10.8”) = 10 parseFloat(a); var b = ‘happy’ Number(b);   =   NAN     STRING TO ARRAY var a = ‘happy   ma’ split – 3 methods Without Space a.split(‘’) = [‘h’,’a’,’p’,’p’,’y’,’ ‘,’m’,’a’] With Space /Comma a.split(‘   ’) =[‘happy’,’ma’] With Limit a.split(‘   ’,1) =[‘happy’] ARRAY TO STRING var a = [1,2,3,4,5] join – 3 methods Without Comma a.join(‘’) = ‘12345’ With Comma a.join(‘,’) = ‘1,2,3,4,5’ With Space a.join(‘    ‘) = ‘1 2 3 4 5’   ARRAY TO OBJECT var a = ['a','b','c','d'] var b =Object.assign({},a)   = object { 0: "a", 1: "b", 2: "c", 3: "d" }   OBJECT TO ARRAY     var a = { 0: "a", 1: "b", 2: "c", 3: "d" } Object.keys(a)   = [0,1,2,3] ...