Syntax

1. // comment text 
2. /* multiple line comment text */

Examples

// This is a single-line comment.


/* This is a multiple-line comment. It can be of any length, and 
you can put whatever you want here. */

continue statement

The continue statement terminates execution of the block of statements in a while or for loop, and continues execution of the loop with the next iteration. In contrast to the break statement, it does not terminate the execution of the loop entirely: instead,

• In a while loop it jumps back to the condition.
• In a for loop it jumps to the update expression.

Syntax

continue

Examples

The following example shows a while loop that has a continue statement that executes when the value of i is 3. Thus, n takes on the values 1, 3, 7, and 12.

i = 0; 
n = 0; 
while (i < 5) { 
    i++; 
    if (i == 3) 
        continue;  
    n += i;
} 

for statement

A for loop consists of three optional expressions, enclosed in parentheses and separated by semicolons, followed by a block of statements executed in the loop. The parts of the for statement are:

• The initial expression, generally used to initialize a counter variable. This statement may optionally declare new variables with the var keyword. This expression is optional.
• The condition that is is evaluated on each pass through the loop. If this condition is true, the statements in the succeeding block are performed. This conditional test is optional. If omitted, then the condition always evaluates to true.
• An update expression generally used to update or increment the counter variable. This expression is optional.
• A block of statements that are executed as long as the condition is true. This can be a single statement or multiple statements. Although not required, it is good practice to indent these statements four spaces from the beginning of the for statement.

Syntax

for ([initial expression]; [condition]; [update expression]) {
    statements
}
initial expression = statement | variable declartion

Examples

This simple for statement starts by declaring the variable i and initializing it to zero. It checks that i is less than nine, and performs the two succeeding statements, and increments i by one after each pass through the loop.

for (var i = 0; i < 9; i++) { 
    n += i;

    myfunc(n);
}

for...in statement

The for statement iterates variable var over all the properties of object obj. For each distinct property, it executes the statements in statements.

Syntax

for (var in obj) { 
    statements }

Examples

The following function takes as its argument an object and the object's name. It then iterates over all the object's properties and returns a string that lists the property names and their values.

function dump_props(obj, obj_name) { 
    var result = "", i = "";
    for (i in obj)
        result += obj_name + "." + i + " = " + obj[i] + "\n";
    return result;
} 

function statement

The function statement declares a JavaScript function name with the specified parameters param. To return a value, the function must have a return statement that specifies the value to return. You cannot nest a function statement in another statement or in itself.

All parameters are passed to functions, by value. In other words, the value is passed to the function, but if the function changes the value of the parameter, this change is not reflected globally or in the calling function.

Syntax

function name([param] [, param] [..., param]) {
    statements }

Examples

//This function returns the total dollar amount of sales, when 
//given the number of units sold of products a, b, and c.
function calc_sales(units_a, units_b, units_c) {
    return units_a*79 + units_b*129 + units_c*699
}

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