Function type in javascript

Question

I want to create my own signal emitter or callback storage, call it whatever you want.

Here is what I come up so far:

var DetonationCallback = function detonationCallback() {
    detonationCallback.callbacks = [];
    detonationCallback.add = function(callback) {
        detonationCallback.callbacks.push(callback);
    };
    for(var i = 0; i < detonationCallback.callbacks.length; ++i) {
        callback[i](arguments);
    }
};

Basically I have two problems now which I can not tackle. The first one is how can I move

    detonationCallback.callbacks = [];
    detonationCallback.add = function(callback) {
        detonationCallback.callbacks.push(callback);
    };

outside of the function? And another question is how can I pass all the arguments which were passed into the detonationCallback just in the same order into callback[i]?

Will be grateful for any answer.

Additional info: when done with the implementation of the type I would like to use it as follows:

var callback = new DetonationCallback();

function f1() {

}

function f2(firstArg, secondArg) {

}

callback.add(f1);
callback.add(f2);

callback();

You can't really do this with the new keyword. The new keyword returns a new instance of DetonationCalback. You can't return anything if you're calling a constructor. — frick
– frick, Commented Mar 22, 2018 at 15:18

ControlAltDel · Accepted Answer · 2018-03-22 15:27:24Z

1

First, make detonationCallback an Object

var detonationCallbacks = {};
detonationCallbacks.callbacks = [];
detonationCallback.clear = function() {
    detonationCallback.callbacks = [];
}
detonationCallback.add = function(callback) {
    detonationCallback.callbacks.push(callback);
};

Second, make your detonate a function in detonationCallback

detonationCallback.detonate = function() {
    for(var i = 0; i < detonationCallback.callbacks.length; ++i) {
        this.callback[i](arguments);
    }
};

If you want/need to use new, just create an object prototype for this

edited Mar 22, 2018 at 15:27

answered Mar 22, 2018 at 15:25

ControlAltDel

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2 Comments

yrslvrtfmv Over a year ago

Sounds good. But I still have a problem with passing parameters into callback[i].

ControlAltDel Over a year ago

@yrslvrtfmv you can just use arguments: jtricks.com/javascript_tutorials/varargs.html

tobbr · Accepted Answer · 2018-03-22 15:32:31Z

1

I'm not sure why you wan't to move the add function outside but how about using a class instead?

Also note the use of .apply() to send several arguments with an array.

class DetonationCallback {
    constructor() {
        this.callbacks = [];
    }
      
    add(callback) {
        this.callbacks.push(callback);
    }
      
    call(args) {
        this.callbacks.forEach(function(callback) {
            callback.apply(this, args);
        });
    }
}

var callback = function(arg1, arg2) {
    console.log(arg1, arg2);
}

var callback2 = function(arg1) {
    console.log(arg1);
}

var handler = new DetonationCallback();

handler.add(callback);
handler.add(callback2);
handler.call(['arg1', 'arg2']);

answered Mar 22, 2018 at 15:32

tobbr

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Comments

alexloehr · Accepted Answer · 2018-03-22 15:44:40Z

0

No need to write this yourself:

When using node you can use the built in EventEmitter lib.
https://nodejs.org/api/events.html

There is also a port for the Browser
https://github.com/Olical/EventEmitter

answered Mar 22, 2018 at 15:44

alexloehr

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