How to optimize your JavaScript code
Everyone who writes JS knows that there are many ways to write the same effect. The results can be the same but the steps are different. However, although you have written the effect, the performance of the page has been greatly reduced. Now In the development of scripts, improving script performance is becoming more and more important. How to optimize your JavaScript code? How can we draw the shortest straight line between two points? Today I will give you a summary of how to optimally write your own JavaScript code.
Traditional Web pages do not contain many scripts, at least they do not affect the performance of the Web page too much. However, as Web pages become more and more like applications, scripts have an increasing impact on them. As more and more applications are developed using web technologies, improving script performance becomes increasingly important. Desktop applications typically use a compiler to convert source code into the final binary. The compiler can spend time optimizing as much performance as possible when generating the final application. Web applications don't have that luxury. Because they need to run on multiple browsers, platforms, and architectures, they cannot be fully precompiled. The browser will take the script one at a time and interpret and compile it, but the final application should load as quickly and run as smoothly as a desktop application. It is expected to run on a wide variety of devices, from regular desktop computers to mobile phones.
#Browsers are pretty good at achieving this, and Opera has one of the fastest scripting engines in any browser today. However, browsers also have some limitations, which are what web developers need to pay attention to. To ensure that your web application runs as fast as possible, this might be as simple as swapping a loop, changing one merged style instead of three, or adding only scripts that will actually run.
This article will show you some changes that can improve the performance of web applications, covering ECMAScript - the core language of JavaScript, DOM and file loading.
Tips
ECMAScript
Avoid using eval or Function constructor
Rewrite eval
If you need a function, use function
Don’t use with
Don’t use try-catch-finally in functions that require performance
Isolate the use of eval and with
Try not to use global variables
Pay attention to the implicit replacement of objects
Avoid using for-in in functions that require performance
Use cumulative form to connect strings
Basic operation ratio Calling functions is faster
Pass in functions instead of strings for setTimeout() and setInterval()
DOM
Redraw and reflow
will Minimize the number of reflows
Minimum reflow
Modify the document tree
Modify invisible elements
Measure
One change Multiple styles
Smoothness for speed
Avoid retrieving a large number of nodes
Improve speed through XPath
Avoid modifications when traversing the DOM
Use variables to cache DOM values in scripts
Document loading
Avoid maintaining the same reference between multiple documents
Quick history navigation
Use XMLHttpRequest
Dynamicly create
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