lazyeval

Minimalist Lazy Evaluation JavaSctipt famework

let lazy = (eval) => ((data) => new Proxy(data, {
  set(obj, key, val) {
      obj[key] = val;
      eval(obj);
  }
}))({});

https://github.com/hack2root/lazyeval

Example

• func is a proxy for an empty objct {}
• func calls evaluation function every time you write to existing, new or user defined properties
• func updates internal object and passes it as an argument for every call to evaluation function
• f is a parameter pointing to the internal representation of the external object {}
• c is not evaluated until all requirements for evaluation is met for evaluation function

describe('let func = lazy((f) => { if (f.a && f.b) { c = f.a + f.b } })', function () {
  it('should add two numbers', function () {

    // 1. ARRANGE
    let a = 1;
    let b = 2;
    let c;

    // 2. ACT
    let func = lazy((f) => {
      if (f.a && f.b) { 
        c = f.a + f.b 
      }
    });

    func.a = a;
    func.b = b;

    // 3. ASSERT
    expect(c).to.be.equal(3);
  });
});