Introduction to JavaScript Scripting Programming in MongoDB and getting started with examples _mongodb

Note: The MongoDB version used by the author is 2.4.7.

Examples of Getting Started

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conn = new Mongo ();
db = Conn.getdb ("db-name"); //Select Database
Db.auth ("User-name", "password"); //user authentication

var map = f Unction () {
    Split_result = This.sentence.split ("");
    for (var i in Split_result) {
        var word = Split_result[i ].replace (/(^\s*) | ( \s*$)/g, ""). toLowerCase (); Remove possible spaces on both sides of the word and convert the word to lowercase
        if (word.length!= 0) {
             emit (Word, 1);
       }
   }
}

var reduce = function (key, values) {
    print (key+ ":" +array.sum (values));
    return Array.sum (values);
}

Db.data.mapReduce (
    map,
    Reduce,
    { Out:{merge: "Mr_result"}}
)

Save As Test01.js, run in Terminal:

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$ MONGO Test01.js

The MapReduce results can be viewed in the collection Mr_result after the run is complete.

It is noteworthy that in the JS script if the direct:

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Db.mr_result.find ();

is unable to output the result.

You should use the following method to output the results:

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conn = new Mongo ();
db = Conn.getdb ("Db-name"); Select Database
Db.auth ("User-name", "password"); User authentication

var cursor = Db.mr_result.find ();

while (Cursor.hasnext ()) {
R = Cursor.next ();
Print (r["_id"] + "T" + r["value"]);
}

Save As Test02.js, run:

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$ MONGO Test02.js

The results are as follows:

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a       1
code    1
collection      1
consider        1
contains         1
documents       1
error    1
follow  1
following       3
found   1
get & nbsp;   1
i       2
in      1
Link     1
map-reduce      1
of      1
on& nbsp;     1
operations      1
orders  1
Prototype        1
that    1
the     4
this     1
when    1

Using the load () function

The load () function is used to introduce additional files, which facilitates code reuse. The simplest scenario is to put the code for the database connection operation in a separate file, set up lib in the current directory, and create a file Base_operation.js in the Lib directory, which reads as follows:

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function Baseoperation () {

/*
Connecting to the database, returning the Connection object
*/
This.getdb = function () {
conn = new Mongo ();
db = Conn.getdb ("Db-name");
Db.auth ("User-name", "password");
return DB;
}
}

Create a file test03.js in the current directory, as follows:

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Load ("Lib/base_operation.js");
BO = new Baseoperation ();
db = Bo.getdb ();

var cursor = Db.mr_result.find ();

while (Cursor.hasnext ()) {
R = Cursor.next ();
Print (r["_id"] + "T" + r["value"]);
}

The effect of running test03.js is the same as test02.js.