在功能参数中强制对象结构

Question

I am new to javascript. I have a function taking an object. But how do I make sure caller is following the structure I want in the object. As there is no concept of class in javascript, I can't create a model class and make the caller use it ?

function foo(myObject)
{

}

Whoever is calling should give me

{
  Count,
  [
    {
      FirstName,
      LastName
    },
    {
      FirstName,
      LastName
    },
  ]
}

Answer 1

Well you could simply check the type of object you have received as an argument, and then check if those values are actually there, like so:

function foo(myObject) {
    if (typeof myObject !== 'object') {
        // doesn't match
        return;
    }
    if (typeof myObject.Count === 'undefined') {
        // no count property
    }
}

However, from your question, it seems you would like to make it more fix which kind of object should be sent as an argument, and this you could also do in javascript, by doing for eg:

function MyParamOptions() {
    // define properties here
    this.persons = [];
    Object.defineProperty(this, 'Count', {
        get: function() {
            return this.Names.length;
        },
        set: function() {
            // dummy readonly
        }
    });
}

Then you could instantiate an instance of this class by saying

var options = new MyParamOptions();
options.persons.push({ firstName: 'bla', lastName: 'bla' });

and change a check inside your foo function like

function foo(myObject) {
    if (myObject instanceof MyParamOptions) {
        // here myObject is MyParamOptions, so you can access the persons array, the Count property etc...
    }
}

// and call foo with your MyParamOptions
foo(options);

However this will not throw any warnings at compile time, so people can call your function with any kind of parameter. If you are looking for errors at compile time, you might look into TypeScript or a similar technology that then transpiles your TypeScript code to javascript)