EWD 3 Training Course Part 23: Traversing a Range using DocumentNode Objects

Copyright © 2016 M/Gateway Developments Ltd
EWD 3 Training Course
Part 23
JavaScript Abstraction of Global Storage:
(d) Traversing a Range of Nodes
Rob Tweed
Director, M/Gateway Developments Ltd
Twitter: @rtweed

myIndex("Andrews",103)=""
myIndex("Barton",23)=""
myIndex("Briggs",210)=""
myIndex("Bryant",23)=""
myIndex("Davies",641)=""
myIndex("Davis",13)=""
myIndex("Davis",9112 )=""
myIndex("Douglas",651)=""
myIndex("Ennis",108)=""
Restricting a Loop to Specific Nodes

Just get names starting Br
-Briggs
-Bryant
Then fetch the data record for each instance
of the name

forEachChild( {prefix: 'Br'} , function{..})
Use the control object argument again
This time limit the loop to a prefix

var index = new this.documentStore.DocumentNode('myIndex');
index.forEachChild({prefix: 'Br}', function(nodeName, childNode) {
// limit the traversal to just those child nodes whose names start Br
});

childNode.forEachChild(function(id) {
// get each id for each name beginning Br
});
});

console.log(id);
});
});
210
386
23
5321

Index for an Customer Document
customer(id, property) = value

customer(id, property) = value
customer = {
'386': {
firstName: 'John',
lastName: 'Briggs',
address: '123 Acacia Drive',
// …etc
},
// ….etc
}

customer(386,"firstName")="John"
customer(386,"lastName")="Briggs"
customer(386,"address")="123 Acacia Drive"
Customer document represented
in Global Storage

customer(386,"firstName")="John"
customer(386,"lastName")="Briggs"
customer(386,"address")="123 Acacia Drive"
var customer = new this.documentStore.DocumentNode('customer');
// use id to point to main data record
var address = customer.$(id).$('address').value;
// … etc
});
});

Iterate Prefixes in Reverse Order?

Iterate Prefixes in Reverse Order
var params = {prefix: 'Br', direction: 'reverse'} ;
index.forEachChild(params, function(name, childNode) {
console.log(id);
});
});

console.log(id);
});
});
Control object allows prefix to be
combined with reverse

console.log(id);
});
});
23
5321
210
386

console.log(id);
});
});
23
5321
210
386
Inner loop is in forward direction!

childNode.forEachChild( {direction: 'reverse'} , function(id) {
console.log(id);
});
});
Use the control object to reverse
the inner loop also

childNode.forEachChild( {direction: 'reverse'} , function(id) {
console.log(id);
});
});
Use the control object to reverse
the inner loop also
5321
23
386
210
Now the output is fully reversed

Restricting the Loop to a Range
From: substring 1
To: substring 2
eg: from Briggs to Davis

forEachChild({
range: {
from: 'Briggs',
to: 'Davis'
}
}, function{..})

More likely restriction:
forEachChild({
range: {
from: 'Br',
to: 'Da'
}
}, function{..})
from and to define prefixes within which it returns nodes

or:
forEachChild({
range: {
from: 'B',
to: 'D'
}
}, function{..})
from and to define prefixes within which it returns nodes

var params = {
range: {
from: 'Br',
to: 'Da'
}
};
console.log(id);
});
});

var params = {
range: {
from: 'Br',
to: 'Da'
}
};
console.log(id);
});
}); 210
386
23
5321
641
714
13
8142
9112

Iterating a Range in reverse?

Iterating a Range in reverse
var params = {
direction: 'reverse',
range: {
from: 'Br',
to: 'Da'
}
};
console.log(id);
});
});
Control object allows range to be

EWD 3 Training Course Part 23: Traversing a Range using DocumentNode Objects

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EWD 3 Training Course Part 23: Traversing a Range using DocumentNode Objects