Jquery: Returning Value From Trigger

问题

I am using a trigger call a get a value from custom event but I want it to return a value and its only giving me Object Object when I do the following call:

var user_id=$("#my_div").trigger("get_id", [username]);

My trigger event function looks like this:

$("#my_div").on("get_id", function(e, username){
    var user_id;
    if (username='fred'){
        user_id=1;
    }
    else if(username='mario'){
        user_id=2;
    }
    return user_id;
});

回答1:

You cannot return a value from a trigger, but you can store information in many different ways, one way is using a object as a parameter:

//event
$("element").on("click", function(event, informationObj) {
       informationObj.userId = 2; //you have to access a propery so you can modify the original object
});
//trigger
var informationObj = {userId : 0};
$("element").trigger("click", [informationObj ]); //informationObj.userId === 2

other way is using jQuerys .data() method

//event
$("element").on("click", function() {
     $(this).data("userId", 2); 
});
//trigger
$("element").trigger("click").data("userId") //2

Another thing you can do is modifying a variable that's declared outside the event and then using it after calling the trigger, or storing it as a property in the element that has the event with the this keyword like this:

//inside the event function
this.userId = 2;

//outside the event
$("element").trigger("click").get(0).userId

Hope it helps.

Edit:

Also, take a look at @Arm0geddon answer below, using .triggerHandler(), just beware that it has some side effects, like not bubbling up the DOM hierarchy.

回答2:

What you can do is use .triggerHandler() instead of .trigger(). This will return a value.

var user_id=$("#my_div").triggerHandler("get_id", [username]);

回答3:

A trigger cannot return a response, because it's a callback method.

In addition jQuery have a fluid API, so .trigger() returns always $(this).
You can write $("#my_id").trigger(something).show().on(someelse)...

回答4:

The trigger function doesn't return the value you return from the event handler.

It returns jQuery object...

.trigger( eventType [, extraParameters] ) Returns: jQuery

docs

This was designed so you could write things like this:

$("#my_div").trigger("get_id", [username]).val('foo').css('color', 'red');

回答5:

Try this:

$("#my_div").on("get_id", function(e, username){
    var user_id;
    if (username='fred'){
        user_id=1;
    }
    else if(username='mario'){
        user_id=2;
    }
    return user_id;
});

var user_id=$("#my_div").triggerHandler("get_id", ["username"]);

回答6:

triggerHandler is the correct answer, but it's worth noted as I have not seen it here yet... You can pass another callback along as well, and have your "on" function call the passed callback to set some return value etc. assuming it's better not to wait for some reason.

来源：https://stackoverflow.com/questions/9145347/jquery-returning-value-from-trigger

标签

jquery

triggers