jeradg / ceibo

Ceibo is a JavaScript micro library to model trees that evaluate arbitrary code when accessing its nodes.

Ceibo

JavaScript micro library to model trees that evaluate arbitrary code when accessing its nodes.

The tree is modeled as a plain JavaScript object where each node has an arbitrary getter function. This allows to have a representation of a tree where a subtree is generated on the fly when a node is accessed.

Examples

Let's start by doing the most simple case, the identity case:

var root = Ceibo.create({
  foo: {
    bar: 'baz';
  }
});

console.log(root.foo.bar); // "baz"

You can create special node types called descriptors that allow you to respond to node access:

var root = Ceibo.create({
  foo: {
    isDescriptor: true,

    get() {
      return 'bar';
    }
  }
});

console.log(root.foo); // "bar"

As you can see, a descriptor is a JavaScript object that has a isDescriptor attribute.

You can define a get method or you can declare a value attribute, then the value attribute is going to be used as is:

var root = Ceibo.create({
  foo: {
    isDescriptor: true,

    value(answer) {
      return `The answer to life, the universe and everything is ${answer}`;
    }
  }
});

console.log(root.foo('42')); // "The answer to life, the universe and everything is 42"

descriptors can inspect and mutate the target object by defining a setup method:

var tree = Ceibo.create({
  foo: {
    isDescriptor: true,

    get() {
      return 'bar';
    },

    setup(target, keyName) {
      Ceibo.defineProperty(target, keyName.toUpperCase(), 'generated property');
    }
  }
});

console.log(tree.foo); // "bar"
console.log(tree.FOO); // "generated property"

Note that Ceibo trees are read-only, so you cannot reassign attributes:

var root = Ceibo.create({
  foo: 'bar';
});

root.foo = 'baz'; // => throws an error!

You can redefine how each value type is processed when the Ceibo tree is created:

function buildString(treeBuilder, target, keyName, value) {
  Ceibo.defineProperty(target, keyName, `Cuack ${value}`);
}

var root = Ceibo.create(
  {
    foo: 'first value'
  },
  {
    builder: {
      string: buildString
    }
  }
);

console.log(root.foo); // "Cuack first value"

Redefine how plain objects are processed to generate custom attributes:

function buildObject(treeBuilder, target, keyName, value) {
  var childNode = {
    generatedProperty: 'generated property'
  };

  // define current keyName and assign the new object
  Ceibo.defineProperty(target, keyName, childNode);

  // continue to build the tree recursively
  treeBuilder.processNode(value, childNode, target);
}

var root = Ceibo.create(
  {
    foo: {
      bar: 'baz'
    }
  },
  {
    builder: {
      object: buildObject
    }
  }
);

console.log(tree.generatedProperty); // "generated property"
console.log(tree.foo.generatedProperty); // "generated property"
console.log(tree.foo.bar); // "baz"

You can navigate to parent nodes

var tree = Ceibo.create({
  foo: {
    bar: {
      baz: 'a value'
    }
  }
});

console.log(Ceibo.parent(tree.foo.bar).bar.baz); // "a value"

You can assign custom parents to trees

var parentTree = Ceibo.create({ foo: 'value' });
var childTree = Ceibo.create({ bar: 'another value' }, { parent: parentTree });

console.log(Ceibo.parent(childTree).foo); // "value"

License

Ceibo is licensed under the MIT license.

See LICENSE for the full license text.