AJAX - The Complete Reference

578 Part IV: Appendixes

The following shows a simple example of the use of these statements.

var matchi=3;

var matchj=5;

loopi:

for (var i=0;i<10;i++)

{

if (i != matchi)

continue loopi;

for (var j=0;j<10;j++)

{

if (j==matchj)

break loopi;

}

}

Object Iteration

JavaScript also supports a modification of the for loop (for/in), which is useful for

enumerating the properties of an object:

for ( [ var ] variable in objectExpression ) statement(s)

This simple example here shows for/in being used to print out the properties of

a browser’s window.navigator object:

for (var aProp in window.navigator)

document.write(aProp + "<br />");

JavaScript 1.7’s Generators and Iterators

JavaScript 1.7 also introduces a variety of interesting features, many of which are adapted

from Python features. For example, a generator is a function that does not return a value but

instead returns a yield. When you set the function, it does not execute, but instead binds the

values and sets up an iterator. You can then iteratively loop through the function and each

loop will return the next yield. As you can see from this example, it will hold the state of the

function after each call.

function showYield()

{

var call=1;

yield call;

call++;

yield call;

call++;

yield call;

}

var myGenerator = showYield();

for (var i in myGenerator)

alert(i);

//alerts 1 2 3