JS Second lesson (Loop statement)

1. Conditional statements

1) comparison operator

= =,! =, >, >=, <, <=

Turn case: toUpperCase (), toLowerCase ()

2) Logical operators

and Operations &&

or Operation | |

Non-op!

3) If statement

If (condition)

{ ....}

Else if (condition)

{....}

Else

{....}

Cases:

var iday=number (Prompt ("Please enter Week", ""));
if (IsNaN (Iday))
{
Alert ("Please enter a number");
}
else if (iday<1| | IDAY&GT;7)
{
Alert ("Please enter the correct week");
}
Else
{
Switch (iday)
{
Case 1:
{
Alert ("Monday");
Break
}
Case 2:
{
Alert ("Tuesday");
Break
}
Case 3:
{
Alert ("Wednesday");
Break
}
DEFA ult:
{
Break
}}
}

Prompt (...) input box

Number (..) converted to digital

IsNaN (..) Determines whether the parameter is Nande, Nan is true, and vice versa is False

4) switch

Switch (..)

{

Case: :

{

...

Break

}

Case: :

{

...

Break

}

Default

{

..

}

Cases:

Iweek = parseint (Prompt ("input integer from 1 to 7", ""));
Switch (Iweek) {
Case 1:
document.write ("Monday");
Break
Case 2:
document.write ("Tuesday");
Break
Case 3:
document.write ("Wednesday");
Break
Case 4:
document.write ("Thursday");
Break
Case 5:
document.write ("Friday");
Break
Case 6:
document.write ("Saturday");
Break
Case 7:
document.write ("Sunday");
Break
Default
document.write ("Error");
}

2. Circular statements

1) while

while (...)

{

...

}

Cases:

var i=isum=0;
while (i<=100) {
Isum + = i;
i++;
}
alert (isum);

2) Do.....while

Do

{

...

}

while (...)

Cases:

var anumbers = new Array ();
var smessage = "You have entered: \ n";
var itotal = 0;
var vuserinput;
var iarrayindex = 0;
do{
Vuserinput = Prompt ("Enter a number, or ' 0 ' exit", "0");
Anumbers[iarrayindex] = vuserinput;
iarrayindex++;
Itotal + = number (vuserinput);
Smessage + = vuserinput + "\ n";
}while (Vuserinput! = 0)//exit loop body when input is 0 (default)
Smessage + = "Total:" + itotal;
alert (smessage);

3) for

For (...)

{

....

}

Cases:

for (Var i=1;i<10;i++) {//multiplication table altogether nine rows
document.write ("<tr>");//row is a row of table
for (j=1;j<10;j++) {//each row has 9 cells
if (j<=i)
{//Cells with content
document.write ("<td style= ' border:2px solid #004B8A; Background: #FFFFFF; ' > "+i+" * "+j+" = "+ (i*j) +" </td> ");
}
else//cells with no content
document.write ("<td style= ' Border:none; ></td> ");}
document.write ("</tr>");
}

JS Second lesson (Loop statement)