dust js: aliasing an object not working - dust.js

Question

Template
{#person alias=root}{alias.value}: {name}, {age}{/person}
data:
{
"root": {value:"MR."},
"person": {
"name": "Larry",
"age": 45
}
}
Expected output:
MR. Larry, 45
Actual output:
: Larry, 45
I'm trying to alias an object like shown above. But its not working. Please have a look into this fiddle http://jsfiddle.net/G86mu/1/.
If i replace {value:"MR."} with a string say "root":"Mr." and change my template to
{#person alias=root}{alias}: {name}, {age}{/person}
the output is as expected. Please let me know how do i alias an object

Answer 1

The reason this isn't working is because the context within Dust is not the same as the JSON you pass in to dust.render. Internally, Dust wraps your JSON so that it can include params, globals, and blocks in the context.
So, you are not adding alias to the current context, as you might assume. Instead, you are adding alias one level above your current context. Although the representation isn't exactly accurate, it should be helpful for explanation purposes:
// Incorrect:
{
"root": {
"value": "MR."
},
"person": {
// Current context
"alias": {
"value": "MR."
},
"name": "Larry",
"age": "45"
}
}
// (more) correct:
{
"root": {
"value": "MR."
},
"alias": {
"value": "MR."
"person": {
// Current context
"name": "Larry",
"age": "45"
}
}
}
When the context is viewed in this way, it makes sense why {#person alias=root}{alias.value}: {name}, {age}{/person} will not work. When using the dot-notation inside of a reference (as in {alias.value}, dust starts in the current context and goes down. Since there is no "alias" object inside of the current context, dust gives up, and you get an empty string.
However, if when you don't use the dot-notation, dust starts at the current context and searches up. The first time it finds a match, it will use that match. So, for your example, you could use the following to get your expected output.
{#person alias=root}{#alias}{value}{/alias}: {name}, {age}{/person}
Alternatively, if you could use:
{#person aliasVal=root.value}{aliasVal}: {name}, {age}{/person}