js_basics_3.html

<script>
	/*
	//type casting	
	//to number
	
	var sum = 12 * '12';
	//alert(typeof sum + "\n" + sum);
	
	var anAdd = 12 + 12;
	var anAdd2 = 12 + '12';
	var anAdd3 = '12' + 12;
	
	//alert(anAdd +"\n" + anAdd2 +"\n" + anAdd3 + "\n");
	
	var aPreAdd = 12 + 12 + '12';
	//alert(aPreAdd);
	
	var aPreAdd = '12' + 12 + 12;
	//alert(aPreAdd);
	
	var aPreAdd = 12 + 12 * '12';
	//alert(aPreAdd);
	
	var aPreAdd = 12 + 12 * '12abcd';
	//alert(aPreAdd);
	
	//alert(Number('12abcd'));
	//alert(parseInt('asas12'));
	
	//string
	var aString = 12 +'';
	//alert(typeof aString);
	
	var aUrl = document.location + '';
	//alert(typeof aUrl);
	
	var aUrl = document.location.toString();
	//alert(typeof aUrl + "\n" + aUrl);
	
	//bool
	var aBool = 'aSrting';
	//alert(typeof aBool + "\n" + aBool + "\n" + typeof !!aBool +  "\n" + !!aBool);
	
	//alert(true + "\n" + true );
	//alert(true + false );
	
	//alert( (true + "\n"+ true) && true);
	//alert( true + "\n"+ true && true +"\n"+ true && false +"\n"+ false && true + "\n" + false && false ); 
	//alert( true + "\n"+ (true && true) +"\n"+ (true && false) +"\n"+ (false && true) + "\n" + (false && false) ); 
	var anUndefinedVariable;
	var aNaN = 12 * 'qwqwqw';
	//alert( !!anUndefinedVariable );
	//alert( !!'' );
	//alert( !!"" );
	//alert( !!0 );
	//alert( !! null );
	//alert( !! aNaN );
	//alert( typeof NaN );
	
	//anything else is true	
	alert( typeof {} );
	alert( !! {} );
	
	alert( typeof [] );
	alert( !! [] );
	alert( !! '0');	
	
	if( true ){
		alert('I am in if block');
	}	

	if( false ){
		alert('I am in if block');
	}else{
		alert('I am in else block');
	}
	
	if( true ){
		alert('I am in 1st if block');
	}else if( true ){
		alert('I am in 2nd if block');
	}else{
		alert('I am in else block');
	}
	
	if( false ){
		alert('I am in 1st if block');
	}else if( true ){
		alert('I am in 2nd if block');
	}else{
		alert('I am in else block');
	} 
	
	//advance: block scope
	var a = 'hello: outside if';
	b = 'how are you: outside if';
	if(true){
		var a = 'hello';
		b = 'how r u';
		//let c = 'let xyz';
	}	
	alert(a +"\n"+ b +"\n");
	
	//ternary operator
	
	var a = (true)? 'Ist value' : '2nd value';
	alert(a);
	
	var b = (false)? 'Ist value' : '2nd value';
	alert(b);
	
	
	var aSwitch = '12';
	
	switch( aSwitch ){
		
		case 1:
			alert('I am 1');
			break;
		case 12:
		case '12':
			alert('I am  Number 12 OR String 12');
			break;
		case '123':
			alert('I am string 123');
			break;
		case 'abc':
			alert('I am string abc');
			break;
		default:
			alert( 'I am default'  );
		
	}
	
	
	//Loop
	var counter = 0;
	//exercise 1:  an infinite loop
	for(   ; counter < 5     ;    ){
		
		alert(counter);
	}
	//exercise 2: 
	for(   ; counter < 5     ;  counter++  ){
		
		alert(counter);
	}
	//exercise 3: 
	for( counter = 0; counter < 5     ;  counter++  ){
		
		alert(counter);
	}
	
	var counter = 0;
	while(counter < 5 ){
		
		alert(counter);
		counter++
	}
	*/
	//first execute and then check the condition
	
	/*var counter = 0;
	do{
		alert(counter);
		counter++
	}while(counter < 5);
	
	
	for( counter = 0; counter < 5 ;  ){		
		//alert(counter++);
		alert(++counter);
	}
	
	
	var anObj = {
		a:'a string',
		b:12
	}
	
	//list all properties and methods/functions of window object
	//anObj = this;
	
	for(i in anObj){
		document.write( i + ": "+ anObj[i] +"<br />");
		//document.write( i + ": "+ eval(anObj+'.'+i) +"<br />");
	}
	
	
	
	//use of continue in a loop
	for( i=0; i < 10; i++ ){
	
		//ex1: print all  numbers
		document.write(i + "<br />");
		
		//OR
		
		//ex2: print odd numbers
		if( i%2 == 1){
			continue;
		}
		document.write(i + "<br />");
	}
	
	
	//use of break in a loop
	for( i=0; i < 10; i++ ){
	
		//ex3: never print more than 3 digits
		if( i > 2 ){
			break;
		}
		document.write(i + "<br />");
	}
	
	
	
	//operators
	
	// Math operators: + , - , * , /, %
	// Concatenation operator: +    :::: note:::: + has 2 roles ( an overloaded operator )
	// logical operator: ! > < >= <=  || &&
	// assignment : = 
	// equality : ==, ===, !=, !==, <>,
	
	var a = 12;
	var b = '12';
	
	if( a == b ){
		alert( 'I am in if block');
	}else{
		alert( 'I am in else block');
	}
	
	if( a === b ){
		alert( 'I am in if block');
	}else{
		alert( 'I am in else block');
	}
	*/
	var xyz;
	var a = xyz || 'none';
	alert(a);
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	

</script>