congruence

Validate the structure of Javascript objects using semantic templates. Written as an underscore/lodash mixin.

congruence

Validate Javascript objects using semantic templates. Written as an underscore/lodash mixin.

$ npm install congruence --save
_.mixin(require('congruence'));
var template = { module: _.isString,   version: semver.valid };
var object =   { module: 'abc', version: 'v1.0.0'     };
assert.isTrue(_.congruent(template, object));

Above, the object is congruent to the template because object.module is a string, and semver.valid[1] returns true for object.version.

It's like regular expressions for Javascript objects. Easily test the structure of Javascript objects using expressive templates. Designed as an lodash mixin.

Use this module to check the congruence of Javascript structures and validity of values using semantic templates. Suppose an object:

var obj = {
  megahertz: 266,
  message: 'hello world'
};

We use the built-in lodash matching functions to build a template (an isometry) that we can validate against. Here is a template that matches obj above:

var matchingTemplate = {
  megahertz: _.isNumber
  message: _.isString
};

But this will not match:

var failedTemplate = {
  megahertz: 500,
  foo: _.isFunction
};

Both properties will fail validation. If a non-function is given in the template value, it will be used as a strict equality check. megahertz is not equal to 500 so that fails. And the template requires foo to be a function, but obj.foo is not even defined.

Any lodash isXYZ function can be used as a predicate; you can also define your own, e.g.

var template = {
  afunction (list) {
    return _.all(list, function (value) {
      return (value % 2) > 0;
    });
  }
},
object = {
  a: [ 1, 3, 5 ]
};
assert.isTrue(_.congruent(template, object));
var object = {
  a: 3.1415926535,
  foo: {
    bar: {
      b: 'hello world',
      c: [ 1, 1, 2, 3, 5, 8 ],
      d: new Date()
    }
  }
};
var matchingTemplate = {
  a: 3.1415926535,
  foo: _.congruent({
    bar: _.congruent({
      b: _.isString,
      c: _.isArray,
      d: _.compose(_.not, _.isFunction)
    })
  })
};
 
assert.isTrue(_.congruent(matchingTemplate, object));
var template = {
  id: 57,
  name: 'Travis'
};
var object = {
  id: 57,
  name: 'Travis',
  color: 'blue',
  foo: 1
};
 
// the extra object properties are ignored 
assert.isTrue(_.similar(template, object));

Return true if the object matches all of the conditions in the specified template, and the keysets are identical.

@paramdescription
templatethe congruence template used to validate the object
objectthe object to validate
@returndescription
Booleantrue if the object is congruent to the template, false otherwise
var template = {
  <key>: <predicate>
};
var object = {
  <key>: <value>
};
 
_.congruent(template, object);

Return true if the object matches all the conditions specified by the template.

@paramdescription
templatethe congruence template used to validate the object
objectthe object to validate
@returndescription
Booleantrue if the object is congruent to the template, false otherwise
var template = {
  <key>: <predicate>
};
var object = {
  <key>: <value>
};

MIT