节点 JS - 将 function 本身发送到客户端，function 在客户端（不在服务器中）运行

Question

I am building a system in nodeJS that the user has to go through lots of forms and after each form the user fills, he sends the form's DATA to the nodeJS server and receives another form according to the data he filled in the previous form.

I have defined in JS files objects that contain all forms. Then each time the user receives JS object that contains the settings of the form.

And there is a code in the client that knows how to create a form by js object. The problem is, some of the data is dynamic according to the behavior of the client.

And I want to send to the client a function that will run on the client (and affect the form). Is there an elegant way to send a function to the client (do not run the function in the server).

I realized that using EVAL is not recommended at all. Also to make sure that all the functions are already in the client, And in the settings file to write only the function name makes it very difficult for me. Is there a convenient way to do this?

For example, attaching Setting Field:

{
    name: 'appleNum',
    type: 'number',
    title: 'How many apples did you eat today',
    Required: true,
    validation: function (value) { 
        if (value >= 0)
            return true; 
    },
    MaxChars: null,
    default: null,
},

I want to send the validation function to the client And to run in the client. thank for all.

Answer 1

I assume that you actually communicate with the client via JSON. JSON and a javascript objects are very different things. JSON just represents the data of a javascript object. It can not hold any methods to be executed.

However there is a possibility to run code on the client side, that you setup on the server. This works with so called remote procedure calls . For node there is a library called eureca.io . Maybe this is of any help to you.

Answer 2

You can convert your function to a string with toString method on server side and you can generate that function from string with a Function constructor on the client side.

Below snippet shows a sample stringification and function generation code

 // lets say a you have a function f function f(value) { if (value >= 0) return true; } // you can convert this function to a string like this var stringified_function = f.toString(); // this string can be safely transferred in a json between client&server console.log(stringified_function); // you can re-create that function from string like this on client side var new_f = new Function("return " + stringified_function)() // now you can use the new function on client side console.log(new_f(0)); // returns true console.log(new_f(3)); // returns true console.log(new_f(-1)); // returns undefined