jQuery Design Patterns

Optimizing common JavaScript code

In this section, we will analyze some performance tips that are not jQuery-specific and can be applied to most JavaScript implementations.

Writing better for loops

When iterating over the items of an array or an array-like collection with a for loop, a simple way to improve the performance of the iteration is to avoid accessing the length property on every loop. This can easily be done by storing the iteration length to a separate variable, declared just before the loop or even along with it, as shown below:

for (var i = 0, len = myArray.length; i < len; i++) { 
    var item = myArray[i]; 
    /*...*/ 
} 

Moreover, if we need to iterate over the items of an array that does not contain falsy values, we can use an even better ...