objdive

Lookup object properties deeply.

API

dive(data[, path[, fallback]])

If path is false-y or missing, returns data. Otherwise, path is converted to a string and split into steps (details below) and dive() descends into deeper levels of data, using each step as a property name to lead its way.

There are two empty values in JavaScript for which property lookup will fail: null and undefined. In case the current level is one of them, dive() will instead use the fallback. If fallback is missing or undefined, it defaults to false in order to make any property lookup succeed (i.e. not crash) and yield undefined. If you want an Error thrown instead, give null (see examples below).

Path syntax

Path splitting has two modes, based on the first character in path (let's call it "p0"):

• If p0 is a letter (A..Z, a..z), digit (0..9) or _, steps will be split by ..
• Otherwise, steps will be split by p0, starting from the 2nd character of path.
• In case you intend to use non-ASCII step separators, keep in mind that JavaScript uses UCS-2 characters. If path begins with a high unicode character (above U+FFFF), it will most likely be represented as a surrogate pair, so p0 will be an unpaired high surrogate character.

Usage

from test/usage.js:

var dive = require('objdive'), x = {
  '': { empty: 'key' },
  foo: 42,
  bar: {
    baz: 23,
    qux: [ 'hello', 'world', 'how', 'are', 'you?' ],
    './|': true
  },
  'bar.baz': 9999,
  'bar.qux': [ 0.1, 0.2, 0.3, 0.4 ],
  '::.@': { hi: 'hello' }
};

equal(dive(x),      x);
equal(dive(x, ''),  x);

equal(dive(x, 'foo'),         x.foo);
equal(dive(x, 'foo.bar'),     x.foo.bar);
equal(dive(x, 'bar'),         x.bar);
equal(dive(x, 'bar.baz'),     x.bar.baz);
equal(dive(x, 'bar.qux.2'),   x.bar.qux[2]);

equal(dive(x, '.bar.baz'),    x.bar.baz);
equal(dive(x, '/bar/baz'),    x.bar.baz);
equal(dive(x, ':bar:baz'),    x.bar.baz);
equal(dive(x, '|bar|qux|2'),  x.bar.qux[2]);
equal(dive(x, '/bar.baz'),    x['bar.baz']);
equal(dive(x, '/bar.qux/2'),  x['bar.qux'][2]);

equal(dive(x, '.'),           x['']);
equal(dive(x, '@'),           x['']);
equal(dive(x, '@bar@./|'),    x.bar['./|']);
equal(dive(x, '?::.@?hi'),    x['::.@'].hi);

equal(dive(x, '.no.such.key'),    undefined);
equal(dive(x, '.toString'),       undefined);
equal(dive(x, '.hasOwnProperty'), undefined);
// Prefer a crash?
fails(function () { dive(x, '.no.such.key', null); },
  /^TypeError: [\S\s]+ null\b/);

// You can also use fancier defaults:
function fancy(path) { return dive(x, path, fancy.fallbackObj); }
fancy.fallbackObj = {
  '': 'index.html',
  '?limit': 9000,
  crash: null
};

equal(fancy('/'),           x['']);
equal(fancy('/foo'),        x.foo);
equal(fancy('/foo/bar'),    undefined);
equal(fancy('/foo/bar/'),   'index.html');
equal(fancy('/foo/?limit'), undefined);
equal(fancy('/foo/?limit'), x.foo['?limit']);
equal(fancy('/404'),        undefined);
equal(fancy('/404/'),       'index.html');
equal(fancy('/404/?limit'), 9000);
equal(fancy('/404/crash'),        null);
equal(fancy('/404/crash/noes'),   undefined);

Known issues

• Versions before 0.1.3 had a flawed fallback implementation that would return methods of false for some keys.

License

ISC