Mastering JavaScript

Server-Side JavaScript
There is a cool trick that I love to use. While installing modules from the command
line, we can add the --save flag to add that module's dependency to the package.
json file automatically:
npm install async --save
npm WARN package.json chapter9@1.0.0 No repository field.
npm WARN package.json chapter9@1.0.0 No README data
async@1.5.0 node_modules/async
In the preceding command, we installed the async module with the normal npm
command with a --save flag. There is a corresponding entry automatically created
in package.json:
"dependencies": {
"async": "^1.5.0",
"request": "^2.65.0"
},
JavaScript performance
Like any other language, writing correct JavaScript code at scale is an involved task.
As the language matures, several of the inherent problems are being taken care of.
There are several exceptional libraries that aid in writing good quality code. For
most serious systems, good code = correct code + high performance code. The demands of
new-generation software systems are high on performance. In this section, we will
discuss a few tools that you can use to analyze your JavaScript code and understand
its performance metrics.
We will discuss the following two ideas in this section:
• Profiling: Timing various functions and operations during script-profiling
helps in identifying areas where you can optimize your code
• Network performance: Examining the loading of network resources such as
images, stylesheets, and scripts
JavaScript profiling
JavaScript profiling is critical to understand performance aspects of various parts of
your code. You can observe timings of the functions and operations to understand
which operation is taking more time. With this information, you can optimize the
performance of time-consuming functions and tune the overall performance of your
code. We will be focusing on the profiling options provided by Chrome's Developer
Tools. There are comprehensive analysis tools that you can use to understand the
performance metrics of your code.
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