cartography
v1.6.0
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Object to Object mapper
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Cartography
Javascript Object to Object mapper
Cartography takes an input Object and translates it into a new Object with a different structure as specified by a schema. It can also be used for validating input structures.
var theInput = {
id: 123,
userName: 'HappyLand',
color: {
definition: '#7ff'
},
day: 'Mon',
month: 'Aug',
}
var theDesiredOutput = {
id: 123,
name: 'HappyLand',
base: {
color: '#7FF',
time: 'Mon - Aug'
}
}
// let's use Cartography
var f = cartography.filters
var theSchemaToTranslateOneIntoTheOther = {
id: [f.required, f.isInteger],
name: ['userName', f.isString],
base: {
color: ['color.definition', f.isString, function(v) {return v.toUpperCase()}],
time: function(inputObject) {return inputObject.day +' - '+ inputObject.month}
}
}
assert.deepEqual(cartography.map(theInput, theSchemaToTranslateOneIntoTheOther), theDesiredOutput)
The schema's structure is the same as that of the output Object: it has the same attribute names and the same nested structure (if any), but each attribute value describes how obtain the final output value.
Each attribute value can be one of three things: a list of filters, another schema Object or a custom function.
Lists of filters are Arrays of filters.
If the name of the desired output attribute does not match the name and path of the source attribute,
a different path string can be specified as the first element of the Array.
This could be any attribute name ('address'
, 'id'
, 'account'
) or path to a
nested attribute ('account.emailAddress'
, 'permissions.write.quota'
).
A filter can be any function that accepts a single argument as its input value and returns the transformed value. Filters are executed on the input value one after the other.
When the input is not valid, a filter can throw a CartographyError
:
CartographyError
s are collected by the map
method and decorated with the
full path of the input value that caused the error.
A convenient way to create validation filters is to use the .filters.assert
factory.
Custom functions are passed the input Object as argument and their output is used as final value for the output attribute.
var cartographyCarSchema = {
manifacturer: function(){return 'Adslot'},
name: function(car){return car.model +' '+ car.variant}
}
MAIN API
map(source, schema)
Translates the source
object according to the given schema
and returns the result.
Any field of the schema whose final value is undefined
will not appear in the result.
If no fields have defined values, map
will return undefined
rather than an empty Object.
mapArray(source, schema, [arrayFilters])
Translates all elements the source
array according to the given schema
and returns the result.
The schema
can be an array of filters or a schema (that applies to an array of objects).
The optional arrayFilters
is an array of filters that apply to the source array before
the translation of the elements.
CartographyError(message)
This is the error that should be thrown when a filter encounters an invalid value. Cartography will add the full path of the invalid input to the error message.
isCartographyError(object)
Returns true
if the given argument is a CartographyError
.
FilterChainBreak(finalValue)
Is a special Error used to interrupt the chain of filters.
If a filter throws this, all subsequent filters are ignored and the final attribute value
is set to finalValue
.
FilterChainBreak
is used internally by filters.optional
and filters.default
.
from(sourcePath, filters...), same(filters...)
These are two helpers to create lists of filters. They have three main advantages:
- They validate the input
- They flatten nested arrays
- They may or may not look nicer than Arrays in CoffeeScript
{from, same, filters: {required, isString}} = cartography
theSchemaToTranslateOneIntoTheOther =
id: same required, isInteger
name: from 'userName', isString
base:
color: from 'color.definition', isString, (v) -> v.toUpperCase()
time: (inputObject) -> "#{inputObject.day} - #{inputObject.month}"
Built-in filters
filters.optional
If the value is null
or undefined
it will directly assign undefined
to the target attribute,
preventing any subsequent filter from being executed on the value.
Otherwise, it will pass the value as it is to the next filter.
filters.defaults(defaultValue)
If the value is null
or undefined
it will directly assign defaultValue
to the target attribute,
preventing any subsequent filter from being executed on the value.
Otherwise, it will pass the value as it is to the next filter.
filters.required
Throws if the value is null
or undefined
.
filters.array(filters...)
var input = {
aListOfStuff: [1, 4, 5]
}
var schema = {
list: ['aListOfStuff', filters.array(filters.isInteger, function(n){return n+'.0'})]
}
var expectedOutput = {
list: ['1.0', '4.0', '5.0']
}
assert.deepEqual(cartography.map(input, schema), expectedOutput)
filters.array
ensures that the value is an Array and applies the specified filters
, if any, to each element of the value.
If filters
contain any nested Array, they will be flattened.
filters.object(schema)
var input = {
someHash: {
a: 1,
b: 'hello!',
c: ['blue', 'black'],
}
}
var schema = {
keys: ['someHash', filters.object({
a: [filters.isNumber],
b: [filters.isString, function(s) {return '**'+ s +'**'}],
c: [filters.array(filters.isString)]
})]
}
var expectedOutput = {
keys: {
a: 1,
b: '**hello!**',
c: ['blue', 'black']
}
}
assert.deepEqual(map(input, schema), expectedOutput)
filters.object
creates a filter that passes the value through cartography.map
with the given nested schema.
filters.assert(condition, errorMessage)
var isEven = filters.assert(function(n){return n % 2 === 0}, 'must be even')
Returns a filter that asserts for the given condition, producing a CartographyError
with the provided
message if the condition is not met.
filters.parseJSON
Converts a JSON string into a JavaScript Object.
filters.isString
Throws if the value is not a primitive string.
filters.isNumber
Throws if the value is not a primitive number.
filters.isInteger
Throws if the value is not an integer and a primitive number.
filters.isOneOf(list)
isPrimaryColor = filters.isOneOf ['red', 'green', 'blue']
Returns a filter that checks whether the value belongs to the given list.