Improving Loop Performance with Local Variables
One effective strategy to enhance the efficiency of a loop is to decrement the iterator towards 0 instead of incrementing towards the total length. Implementing this simple adjustment can lead to significant savings, potentially reducing the original execution time by up to 50%, depending on the complexity of each iteration.
Source:
- To optimize performance, consider storing the value of
nodes.length as a local variable to avoid recalculating it in each iteration.
- You can also increase efficiency by assigning
nodes.get(i) to a local variable if you frequently access that data.
- If the order of operations is irrelevant, contemplate decrementing the for loop towards 0 rather than counting upwards.
- It's worth noting that jQuery's
each() loop tends to be slightly slower compared to manual iteration. For a comparison, refer to this link.
For a straightforward illustration, check out this example:
In the example provided, I have condensed the loop using a while loop:
var nodes = $(".rr span");
var i = nodes.length;
while(i--){
if(i%2 === 0){
nodes.get(i).style.color = "blue";}
}
Observe how the while loop decreases i with each iteration. Hence, when i = 0, the loop terminates because while(0) evaluates to false.
Optimizing Array Processing through Chunking
The chunk() function is designed to segment an array into smaller parts for efficient processing. It takes three parameters: a list of items to process, the processing function for each item, and an optional context variable to define the value of 'this' within the processing function. By introducing timers between processing stages (e.g., every 100ms), the function removes and processes one item at a time until all items are dealt with.
If you require a method to execute loops in sections to prevent browser crashes, explore Nick Zakas's chunk method outlined here.
function chunk(array, process, context){
setTimeout(function(){
var item = array.shift();
process.call(context, item);
if (array.length > 0){
setTimeout(arguments.callee, 100);
}
}, 100);
}
Enhancing Performance with createDocumentFragment()
By utilizing the document fragment concept, changes made off the main DOM tree do not trigger page reflow, leading to improved performance outcomes. Document fragments are universally supported across browsers, including Internet Explorer 6, making them a versatile tool for enhancing web application speed.
Reflow refers to the computation of layout engine formatting objects' geometry during rendering.
Since iterative display property adjustments prompt window repaints, consider using createDocumentFragment to minimize repainting requirements. By consolidating all modifications within the fragment before updating the DOM, you reduce unnecessary repaint cycles.