ctxobj

Adds immutable context to objects. Good for contextual logging.

ctxobj.new(obj)

Decorates obj with a context. pushctx or popctx will create a child-object with the extended context. Child objects maintains an invisible link to parents.

var ctxobj = require('../main');

// just an object
var obj0 = { x: 1, y: { val: 2 } }

// decorate with context
var obj1 = ctxobj.new(obj0)

// create child objects by pushing and poping data to the context
var obj2 = obj1.pushctx('c1')
var obj3 = obj2.pushctx('c2a').pushctx('c2b')
var obj4 = obj1.pushctx('c3')
var obj5 = obj3.popctx().popctx();

// this will only change 'x' on obj5
obj5.x = 99;

// this will change y.val on all the objects (because we are not setting `y` itself)
obj5.y.val = 99;

Output:

obj0 --> { x: 1,  y: { val: 99 }, ctx: undefined }
obj1 --> { x: 1,  y: { val: 99 }, ctx: [] }
obj2 --> { x: 1,  y: { val: 99 }, ctx: [ 'c1' ] }
obj3 --> { x: 1,  y: { val: 99 }, ctx: [ 'c1', 'c2a', 'c2b' ] }
obj4 --> { x: 1,  y: { val: 99 }, ctx: [ 'c3' ] }
obj5 --> { x: 99, y: { val: 99 }, ctx: [ 'c1' ] }

ctxobj.console(console)

Decorates console-like objects with a context that is prepended to each console.xxx() call.

var ctxobj = require('ctxobj');

var log0 = ctxobj.console(console);
log0.info('no context yet');

var i = 0;
var log1 = log0.pushctx('c1').pushctx(function() { return i++; });
log1.warn('now with a two items in the context');
log1.info('yo yo yo');

var log2 = log1.popctx();
log2.error('only one item in the context now');

Output:

no context yet
[c1] [0] now with a two items in the context
[c1] [1] yo yo yo
[c1] only one item in the context now

Some sugar:

ctxobj.timestamp()

Pushes a timestamp function to the context

ctxobj.stacktop(skip)

Pushes file name and line number of log line to the context (skipping skip frames).

ctxobj.object(parent)

Creates a child object from to parent. The child object is linked to that parent object via it's prototype, so properties of the parent object are available through the child.

Inspired by Douglas Crockford’s parasitic inheritence.

Licence

MIT