1.
Copyright © 2016 M/Gateway Developments Ltd
EWD 3 Training Course
Part 24
JavaScript Abstraction of Global Storage:
(e) Traversing a Document's Leaf
Nodes
Rob Tweed
Director, M/Gateway Developments Ltd
Twitter: @rtweed

2.
Copyright © 2016 M/Gateway Developments Ltd
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachChild(function(nodeName, childNode) {
childNode.forEachChild(function(nodeName, childNode) {
childNode.forEachChild(function(nodeName, childNode) {
// do something with innermost node
});
});
});
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Nested forEachChild() Loops
Exhaustive traversal of all nodes in document

3.
Copyright © 2016 M/Gateway Developments Ltd
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachChild(function(nodeName, childNode) {
childNode.forEachChild(function(nodeName, childNode) {
childNode.forEachChild(function(nodeName, childNode) {
// do something with innermost node
});
});
});
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Nested forEachChild() Loops
Exhaustive traversal of all nodes in document
This example requires 11 iterations

4.
Copyright © 2016 M/Gateway Developments Ltd
Traversing Leaf Nodes?
• Leaf Nodes are DocumentNodes that have
a value and no child nodes

5.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes

6.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes

7.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes

8.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes

9.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes
Just 8 iterations to exhaustively traverse the example

10.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes
Just 8 iterations to exhaustively traverse the example
We can use another DocumentNode Method:
forEachLeafNode()

11.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachLeafNode(function(value, leafNode) ;
console.log(value);
});

12.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachLeafNode(function(value, leafNode) ;
console.log(value);
});
123
foo
foo2
bar1a
bar2a
bar1b
bar2b
bar3b

13.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachLeafNode(function(value, leafNode) ;
console.log(value);
});
Leaf Node's Value

14.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachLeafNode(function(value, leafNode) ;
console.log(value);
});
DocumentNode Object for the Leaf Node

15.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachLeafNode(function(value, leafNode) ;
// how to get the properties/subscripts array for the node?
});

16.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachLeafNode(function(value, leafNode) ;
console.log(JSON.stringify(leafNode._node.subscripts));
});

17.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachLeafNode(function(value, leafNode) ;
console.log(JSON.stringify(leafNode._node.subscripts));
});
['a']
['b', 'c1']
['b','c2']
['d', 'e1', 'f1a']
['d', 'e1', 'f2a']
['d', 'e2', 'f1b']
['d', 'e2', 'f2b']
['d', 'e2', 'f3b']

18.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Terminating Early
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachLeafNode(function(value, leafNode) ;
if (leafNode._node.subscripts[0] === 'd') return true;
console.log(value);
});
return true from the callback function
to terminate prematurely

19.
Copyright © 2016 M/Gateway Developments Ltd
myDoc("a")=123
myDoc("b","c1")="foo"
myDoc("b","c2")="foo2"
myDoc("d","e1","f1a")="bar1a"
myDoc("d","e1","f2a")="bar2a"
myDoc("d","e2","f1b")="bar1b"
myDoc("d","e2","f2b")="bar2b"
myDoc("d","e2","f3b")="bar3b"
Iterating through Leaf Nodes
var doc = new this.documentStore.DocumentNode('myDoc');
doc.forEachLeafNode(function(value, leafNode) ;
console.log(value);
});
Much faster than nested loops if you need
to exhaustively traverse every node in a
large, deepy-nested Document