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Flip your loops

Keep these algorithms in mind when trying to optimize your code. Here are a couple basic rules for

using the correct algorithms:

Whenever possible, use local variables or numerically indexed arrays instead of named properties.

If a named property is going to be used more than once, store its value in a local variable to

avoid running a linear algorithm each time the value is needed.

Reverse your loops

Loops account for a large amount of processing in most programming languages, so keeping them effi-

cient can greatly decrease execution time. A well-known strategy in programming is to iterate through

loops in reverse, starting at the last item and working back to the first. Here’s a regular

for

loop:

for (var i=0; i < aValues.length; i++) {

//do something here

}

To reverse this, start the iterator (

) at the last item in the array, which is in position

aValues.length-1

;

then check to see if

greater than or equal to

and decrement

instead of incrementing it:

for (var i=aValues.length-1; i >= 0; i--) {

//do something here

}

Reversing the loop helps by reducing the complexity of algorithms. It uses a constant value (0) as the

control statement for the loop to reduce the execution time.

Flip your loops

You can replace

while

loops with

do..while

loops to further decrease execution time. Suppose you

have the following

while

loop:

var i=0;

while (i < aValues.length) {

//do something here

i++;

}

The previous code can be rewritten using a

do..while

loop without changing its behavior:

var i=0;

For further information on Big O Notation and computer science algorithms, please refer

to “Big O Notation” from the Wikipedia, available at

http://en.wikipedia.org/

wiki/Big_O_notation

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