History of v8

• v8 is a open source JavaScript engine
• It was developed by Google in 2008 for Google Chrome and Chromium-based browsers
• It is written in C++.
• It translates our JavaScript source code into machine instructions.
• It actually provides a runtime environment in which JavaScript executes.
• The JavaScript engine is independent of the browser in which it executes.

Relation between Node.js and V8

Node.js is referred to as a runtime environment, which includes everything you need to run a program written in JavaScript. V8 is the core thing that powers Node.js. Beside the V8 engine the Node.js runtime environment adds many Node APIs to power the Node.js environment.

V8 is an independentC++ library. It exposes an API that other code can use. If we have C++ program, we can embed V8 in it and run a JavaScript program. Currently node.js can't work without v8. The native bindings of node.js rely on the V8 interface between C++ and JavaScript.

v8 JS engine is used ,

👉 to build Node.js for server-side coding.

👉 to create desktop framework Electron.

👉 by JSON based No-SQL databases like Couchbase and MongoDB.

👉 to power Deno, the latest server-side runtime environment.

A JavaScript Engine is an interpreter which executes JavaScript code. There are 2 ways to create JS engine.

☝ Implement as a standard interpreter.

✌ Just-in-time (JIT) compilation (which converts JS code to machine code)

V8 uses JIT compilation.

Methods in V8

The node:v8 module exposes APIs that are specific to the version of V8 built into the Node.js binary. It can be accessed( importing v8 module) using:

const v8 = require('node:v8')
// or
const v8 = require('v8')
// Both node:v8 , v8 are same

v8.cachedDataVersionTag()

• Used to get a version tag derived from the V8 version, command-line flags, and detected CPU features.
• Returns an integer.
• The data carried by CachedData may depend on the exact V8 version number or current compiler flags.

Syntax

v8.cachedDataVersionTag()

Example

// import v8 module
const v8 = require('v8');

console.log(v8.cachedDataVersionTag()); // Ans : 844655377

// when flags are toggled
v8.setFlagsFromString('--allow_natives_syntax');
console.log(v8.cachedDataVersionTag()); // Ans 2256857713

v8.setFlagsFromString(flags)

• This method is used to set the command line flags for v8 in a programmatic way.
• In this method flags should be string.
• We have to be cautious, when we use this method.
• Any uncertainty may lead to data lose, crashes or it may do nothing.

Syntax

v8.setFlagsFromString(flags)

Example

const v8 = require('v8');

// set command line flag
// flag should be string.
v8.setFlagsFromString('--harmony'); //To fix the regex Lookbehind issue

Some of the flags in v8

• --use_strict (enforce strict mode)
• --expose_gc (expose gc extension)
• --trace_gc (print one trace line following each garbage collection)

v8.getHeapCodeStatistics()

• Used to get statistics about code and its metadata in the heap.
• Returns an object.
• The object contains some properties which holds value in the form of number.

Syntax

v8.getHeapCodeStatistics()

Example

console.log(v8.getHeapCodeStatistics()); 

// Output
{
  code_and_metadata_size: 130888,
  bytecode_and_metadata_size: 111032,
  external_script_source_size: 298712
}

v8.getHeapStatistics()

• Used to get statistics about heap derived from the v8 version.
• Returns object.
• All properties in the returned object hold values as numbers.

Syntax

v8.getHeapStatistics()

console.log(v8.getHeapStatistics());

// Output
{
  total_heap_size: 4931584,
  total_heap_size_executable: 524288,
  total_physical_size: 4931584,
  total_available_size: 2194643104,
  used_heap_size: 4077120,
  heap_size_limit: 2197815296,
  malloced_memory: 254064,
  peak_malloced_memory: 100384,
  does_zap_garbage: 0,
  number_of_native_contexts: 1,
  number_of_detached_contexts: 0
}

v8.serialize(value)

• Used to serialize JavaScript values in a way that is compatible with the HTML structured clone algorithm. The format is backward-compatible also.
• This method needs one parameter (value).
• Value may be any type of data like number, string etc.
• It returns buffer.
• To serialize value into a buffer, DefaultSerializer is used.

Syntax

v8.serialize(value)

Example

// value is string
console.log(v8.serialize('serialize'));
// output :<Buffer ff 0d 22 09 73 65 72 69 61 6c 69 7a 65>

//value is number
console.log(v8.serialize(4532));
//output :<Buffer ff 0d 49 e8 46>

v8.deserialize(buffer)

• Used to deserialize a buffered data into JS value.
• It needs buffer as parameter.
• Returns JS value.
• `DefaultDeserializer is used for deserializing.

Syntax

v8.deserialize(buffer)

Example

console.log(v8.deserialize(v8.serialize('serialize')));
// output : serialize

console.log(v8.deserialize(v8.serialize(4532)));
// output : 4532

Along with the v8 methods we have seen above , There are more methods available in v8. You can refer them here 👉 v8|Node js.

Thank You for reading. 🤗🤗🤗