HellMagic

1.快速理解记忆各种操作符，怎么高效地查阅文档。
比较操作符：
  op.$gt
  op.$gte
  op.$lt
  op.$lte
  op.$eq
  op.$ne
  op.$in
  op.$nin

HellMagic

关于$in操作符的使用，官方有这么描述：
The $in operator selects the documents where the value of a field equals any value in the specified array.注意这里提到"any 
value"，即如果有document为{qty:[5, 10, 15]}，使用db.test.find({qty: {"$in": [10, 1, 3]}})也能找到此document，因为此document的
qty数组对应的值中有一个10在提供的[10, 1, 3]数组中。

示例：db.inventory.find( { qty: { $in: [ 5, 15 ] } } )，等价于 db.invertory.find({"$or":[{qty: 5}, {qty: 15}]})，只不过
当前$or的条件作用的field是同一个field--qty--所以可以使用$in来替代。

$elemMatch的使用
示例：db.scores.find({ results: { $elemMatch: { $gte: 80, $lt: 85 } } })

HellMagic

#
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#  "   # "m m m" #"  #  #   "  #" "#  # # #  #"  # 
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#  "mm"#   # #   "#mm"  "mmm"  "#m#"  # # #  "#mm" 
# 
# nginx configuration For Ruby/Rack web applications
#
# Cooked up with style, care and a bit of *secret*
# nerdy spice. :-)

HellMagic

Essential JavaScript Links

A very exclusive collection of only must-have JavaScript links. I'm only listing my favorite links. Nothing else makes the cut. Feel free to suggest links if you think they're good enough to make this list. The really curious should feel free to browse the comments to find other links. I can't guarantee the quality of links in the comments.

Full Disclosure

Some of these links are affiliate links, meaning that if you make a purchase, I might earn a little money. This has absolutely no bearing on whether or not links make the list. None, whatsoever. However, it does allow me more resources to fight poverty with code. Every little bit counts.

Required Reading (Online resources)