Certainly! Let's break down the provided code snippets:

1. What is it and why is it used?

In Mongoose, a schema is a blueprint for defining the structure of documents within a collection. When you define a schema, you can also attach methods to it. These methods become instance methods, meaning they are available on the individual documents (instances) created from that schema.

Instance methods are useful for encapsulating functionality related to a specific document or model instance. They allow you to define custom behavior that can be executed on a specific document. In the given example, the findSimilarTypes method is added to instances of the Animal model, making it easy to find other animals of the same type.

2. Syntax:

Using methods object directly in the schema options:

javascript const animalSchema = new Schema( { name: String, type: String }, { methods: { findSimilarTypes(cb) { return mongoose.model('Animal').find({ type: this.type }, cb); } } } );

Using methods object directly in the schema:

javascript animalSchema.methods.findSimilarTypes = function(cb) { return mongoose.model('Animal').find({ type: this.type }, cb); };

Using Schema.method() helper:

javascript animalSchema.method('findSimilarTypes', function(cb) { return mongoose.model('Animal').find({ type: this.type }, cb); });

3. Explanation in Simple Words with Examples:

Why it's Used:

Imagine you have a collection of animals in your database, and you want to find other animals of the same type. Instead of writing the same logic repeatedly, you can define a method that can be called on each animal instance to find similar types. This helps in keeping your code DRY (Don't Repeat Yourself) and makes it easier to maintain.

Example:

```javascript const mongoose = require('mongoose'); const { Schema } = mongoose;

// Define a schema with a custom instance method const animalSchema = new Schema({ name: String, type: String });

// Add a custom instance method to find similar types animalSchema.methods.findSimilarTypes = function(cb) { return mongoose.model('Animal').find({ type: this.type }, cb); };

// Create the Animal model using the schema const Animal = mongoose.model('Animal', animalSchema);

// Create an instance of Animal const dog = new Animal({ type: 'dog', name: 'Buddy' });

// Use the custom method to find similar types dog.findSimilarTypes((err, similarAnimals) => { console.log(similarAnimals); }); ```

In this example, findSimilarTypes is a custom instance method added to the Animal schema. When you create an instance of the Animal model (e.g., a dog), you can then call findSimilarTypes on that instance to find other animals with the same type. The method uses the this.type property, which refers to the type of the current animal instance. This allows you to easily reuse the logic for finding similar types across different instances of the Animal model.

hashie

Probaly still prefer: https://github.com/hashie/hashie over this

This doesn't actually seem to be an example of destructure/splat. (When it said "destructure the contents ... out to a block", I was surprised and confused, because splatting is when you splat it into an argument or another hash — never a block.)

An example of destructure/splat would be more like

method_that_takes_kwargs(**symbol_mash)

La colección (o contenedor) del STL que guarda pares ordenados key/value en un hash table se llama el unordered map.

hash the source/destination IP:port tuples to the same worker thread.

http://geohash.org/c216ne:Mt_Hood http://geohash.org/?q=45.37,-121.7&format=gpx http://geohash.org/?q=45.37,-121.7&format=url&redirect=0

• osm — open the location in OpenStreetMaps
• gmaps — open the location in Google Maps
• gc — go to the nearest geocaches in Geocaching.com
• gpx — go directly to GPX download page
• garmin — go directly to Garmin download page
• text — show coordinates as plain text
• url — show Geohash URL as plain text
• maxlen — maximum length of the Geohash

hash://sha256/9f86d081884c7d659a2feaa0?type=text/plain#top \__/ \____/ \______________________/ \_____________/ \_/ | | | | | scheme algorithm hash query fragment

Collision reduction in Hash Tables : Open Addressing

Didn't understand it at first, but now I think it's a pretty clever/decent solution.

Just a bit more verbose than one might like...

At first I had reservations about the fact that this requires you to pass a hash ... or rather, once you start using a hash as your "list", you can't just "switch back" to an array (a "problem" I've noticed in RSpec, where you have some tags that are symbols, and some that are hashes: you have to list the symbols first: describe 'thing', :happy_path, driver: :chrome):

{}.bury(users: Array, 0, 'Value')

But I think that's okay in practice. Just use a hash for all "elements" in your list:

{}.bury(users: Array, 0 => 'Value')

No docs?!

[ Some docs here; First saw it here: ] https://bugs.ruby-lang.org/issues/11747#note-7

equivalent in javascript:

{a, b, ...rest} = {a: 1, b: 2, c: 3, d: 4}

Not a bad replacement for that! I still find javascript's syntax a little more easily readable and natural, but given that we can't use the same syntax (probably because it would be incompatible with existing syntax rules that we can't break for compatibility reasons, unfortunately), this is a pretty good compromise/solution that they've come up with.

具体实现：

#!/usr/bin/python

import glob
import os
import sys

from PIL import Image

EXTS = 'jpg', 'jpeg', 'JPG', 'JPEG', 'gif', 'GIF', 'png', 'PNG'

def avhash(im):
    if not isinstance(im, Image.Image):
        im = Image.open(im)
    im = im.resize((8, 8), Image.ANTIALIAS).convert('L')
    avg = reduce(lambda x, y: x + y, im.getdata()) / 64.
    return reduce(lambda x, (y, z): x | (z << y),
                  enumerate(map(lambda i: 0 if i < avg else 1, im.getdata())),
                  0)

def hamming(h1, h2):
    h, d = 0, h1 ^ h2
    while d:
        h += 1
        d &= d - 1
    return h

if __name__ == '__main__':
    if len(sys.argv) <= 1 or len(sys.argv) > 3:
        print "Usage: %s image.jpg [dir]" % sys.argv[0]
    else:
        im, wd = sys.argv[1], '.' if len(sys.argv) < 3 else sys.argv[2]
        h = avhash(im)

        os.chdir(wd)
        images = []
        for ext in EXTS:
            images.extend(glob.glob('*.%s' % ext))

        seq = []
        prog = int(len(images) > 50 and sys.stdout.isatty())
        for f in images:
            seq.append((f, hamming(avhash(f), h)))
            if prog:
                perc = 100. * prog / len(images)
                x = int(2 * perc / 5)
                print '\rCalculating... [' + '#' * x + ' ' * (40 - x) + ']',
                print '%.2f%%' % perc, '(%d/%d)' % (prog, len(images)),
                sys.stdout.flush()
                prog += 1

        if prog: print
        for f, ham in sorted(seq, key=lambda i: i[1]):
            print "%d\t%s" % (ham, f)

参考代码：

1. http://www.ruanyifeng.com/blog/2011/07/imgHash.txt