v8-flags

Configures v8 flags at runtime.

// use-strict-violator.js
a = "I'm the trouble starter, punking instigator"
 
module.exports = a;

var flags = require('v8-flags').flags;
console.log('inital use strict', flags.use_strict());
 
flags.use_strict(true);
console.log('set use strict to', flags.use_strict());
 
try {
  require('./use-strict-violator');
} catch(err) {
  console.error('FAIL:', err);
}
 
flags.use_strict(false);
console.log('set use strict to', flags.use_strict());
 
var violator = require('./use-strict-violator');
console.log(violator)

inital use strict false
set use strict to true
FAIL: [ReferenceError: a is not defined]
set use strict to false
I'm the trouble starter, punking instigator

Installation

npm install v8-flags

Contributions

I am doing my best to document each flag, but am hoping for others especially the ones with insider knowledge to supply useful comments.

I made this as easy as possible, all you have to do is add/edit the .md file with the name of the flag in this folder and run npm run flag-doc to update all documentation with the added details.

API

The different versions of v8 and thus Node.js have different flags and therefore the API fluctuates somewhat between the versions. The API is generated on install to match the Node.js version you are using.

The flags for the currently latest Node.js versions 0.8, 0.10 and 0.11 are documented in the following locations:

• 0.8
• 0.10
• 0.11

The below API allows to access and configure these flags.

Table of Contents generated with DocToc

• enforceFlagImplications()
• flags()
  • Example
• listFlags() → {Object}
• meta() → {Array.}
• printHelp()
• resetAllFlags()

enforceFlagImplications()

Enforces all flag implications.

Source:

• index.js , lineno 117

flags()

Exposes methods to get and set v8 flags.

Example

var flags = require('v8-flags').flags;
console.log(flags.use_strict()); // false
flags.use_strict(true)
console.log(flags.use_strict()); // true

Source:

• index.js , lineno 21

listFlags() → {Object}

Lists all flags along with their current value.

Source:

• index.js , lineno 85

Returns:

key/value pair for each flag

Type

Object

meta() → {Array.<Object>}

The meta data for the flags.

It is initialized on startup from the definitions found in C++ land.

Source:

• index.js , lineno 39

Returns:

array of objects with the folloing properties each

• name: flag name
• default: default setting of the flag
• type: type of the flag
• description: the description of the flag
• readonly: set true if flag cannot be set
• configurable: set true if setting the flag at runtime has the desired effect
• implications: flags that will be set to true whenever this flag is true and enforceFlagImplications is called
• negativeImplications: flags that will be set to false whenever this flag is false and enforceFlagImplications is called

Type

Array.<Object>

printHelp()

Prints flag help to the console.

Source:

• index.js , lineno 100

resetAllFlags()

Resets all flags to their default values

Source:

• index.js , lineno 108

generated with docme

License

MIT