dotted lookup performance

0-output.txt

$ ./dotted-lookup.js a
new function begin
{ b: { c: 'hello' } }
new function end: 1ms

manual parsing begin
{ b: { c: 'hello' } }
manual parsing end: 0ms
$ ./dotted-lookup.js a.b
new function begin
{ c: 'hello' }
new function end: 2ms

manual parsing begin
{ c: 'hello' }
manual parsing end: 0ms
$ ./dotted-lookup.js a.b.c
new function begin
'hello'
new function end: 0ms

manual parsing begin
'hello'
manual parsing end: 0ms
$ ./dotted-lookup.js a.b.c.d
new function begin
undefined
new function end: 1ms

manual parsing begin
error thrown: no property a.b.c.d found
undefined
manual parsing end: 0ms

1-results.md

1. pure js implementation consistently takes 0ms, whereas new Function fluctuates.
2. manual lookup can also differentiate undefined set on the object, and a property not found

dotted-lookup.js

#!/usr/bin/env node
/**
 * script to test dotted lookups
 *
 * Author: Dave Eddy <dave@daveeddy.com>
 * Date: August 25, 2015
 * License: MIT
 */

var lookup = process.argv[2];
var obj = {
    a: {
        b: {
            c: 'hello'
        }
    }
};



var o;

// new Function
console.log('new function begin');
console.time('new function end');
var func = new Function('return this.' + lookup);
o = func.call(obj);
console.dir(o);
console.timeEnd('new function end');

console.log();

// manual parsing
console.log('manual parsing begin');
console.time('manual parsing end');
try {
    o = dottedLookup(obj, lookup);
} catch (e) {
    console.log('error thrown: %s', e.message);
}
console.dir(o);
console.timeEnd('manual parsing end');

/*
 * lookup the property "str" (given in dot-notation) in the object "obj".
 * "c" is optional and may be set to any delimiter (defaults to dot: ".")
 */
function dottedLookup(obj, str, c) {
    if (c === undefined)
        c = '.';
    var o = obj;
    var dots = str.split(c);
    var s = [];
    for (var i = 0; i < dots.length; i++) {
        var dot = dots[i];
        s.push(dot);
        if (!hasOwnProperty.call(o, dot))
            throw new Error('no property ' + s.join(c) + ' found');
        o = o[dot];
    }
    return o;
}