Javascript custom object needs to listen to another custom objects event

Question

I'm trying to have a custom object listen to an event of another custom object. How can I do this? I've made a small example of a patient and a nurse. When patient screams the nurse needs to pick up the phone and call 911.

function Patient(name) {
    this.Name = name;

    this.Scream = function (terribleSound) {
        alert(terribleSound);
        if (typeof this.OnScream === "function") {
            setTimeout(this.OnScream(this), 1);
        }
    }
}

function Nurse(name, patient) {
    this.Name = name;
    this.Patient = patient;

    this.Patient.OnScream = function (sender) {
        alert(sender.Name + ' screamed');
    }
}

var patient = new Patient('John');
var nurse = new Nurse('Jane', patient);
patient.Scream('AAAAAAAHHHHHHHHhhhhhh!');

This works but now I want to have the name of the nurse inside the alert like:

alert(this.Name + ' heard ' + sender.Name + ' scream.');

But this is the same as the sender and it outputs: "John heard John scream.". That's quite fine but I wanted Jane to hear John scream. How can I solve this JavaScript puzzle?

Best regards, Rémy Samulski

MysterX · Accepted Answer · 2017-03-03 09:38:52Z

1

I don't think you need a timeout in Scream function. But if you do, look at this:

this.Scream = function (terribleSound) {
    alert(terribleSound);
    if (typeof this.OnScream === "function") {
        setTimeout(function(){this.OnScream(this)}.bind(this), 1);
    }
}

If you don't need timeout:

this.Scream = function (terribleSound) {
    alert(terribleSound);
    if (typeof this.OnScream === "function") {
        this.OnScream(this);
    }
}

UPD

Now I have found the solution. You need to pass context of Nurse to patient's OnScream.

Try this one:

function Nurse(name, patient) {
    this.Name = name;
    this.Patient = patient;

    this.Patient.OnScream = function (sender) {
        alert(this.Name + ' heard ' + sender.Name + ' scream.');
    }.bind(this);
}

or with closure:

function Nurse(name, patient) {
    var self = this;
    this.Name = name;
    this.Patient = patient;

    this.Patient.OnScream = function (sender) {
        alert(self.Name + ' heard ' + sender.Name + ' scream.');
    };
}

edited Mar 3, 2017 at 9:38

answered Mar 2, 2017 at 14:06

MysterX

2,3781 gold badge14 silver badges12 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

LiQuick.net Over a year ago

Thx for your suggestions. Have tried both examples but still only John hears himself scream and Jane still doesn't hear John scream. I used the timeout to wait until the this.Scream function ended before Jane's onScream reaction to it. When I don't use the timeout the "event" is already triggered before ending the actual this.Scream.

LiQuick.net Over a year ago

Thank you very much, both solutions work. I'll have a look what this bind() function does. THX!

Collectives™ on Stack Overflow

Javascript custom object needs to listen to another custom objects event

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related