I have this simple code :

console.log('calling doWork func...')
doWork('a', 'b', myCb);

function doWork(param1, param2, callback)
{
        console.log('in func')
        callback();
}


function myCb(a)
{
        console.log('in callback... for value ' + a)
}

I'm running the function with a callback function -

The output I get is :

"calling doWork func..."
"in func"
"in callback... for value undefined"    // notice the undefined

All ok.

Now, I want the callback to be called with a specified param - something like ( which is incorrect since the () is executing the func) :

doWork('a', 'b', myCb('xxxx'));

I want the output to be :

in callback... for value  xxxx

How do I send a parameter with the myCb call in doWork('a', 'b', myCb);? ( 'when you run the callback function , please run it according to value xxxx')

any help ?

p.s. I want to avoid any global flags solution

thanks.

I have this simple code :

console.log('calling doWork func...')
doWork('a', 'b', myCb);

function doWork(param1, param2, callback)
{
        console.log('in func')
        callback();
}


function myCb(a)
{
        console.log('in callback... for value ' + a)
}

I'm running the function with a callback function -

The output I get is :

"calling doWork func..."
"in func"
"in callback... for value undefined"    // notice the undefined

All ok.

Now, I want the callback to be called with a specified param - something like ( which is incorrect since the () is executing the func) :

doWork('a', 'b', myCb('xxxx'));

I want the output to be :

in callback... for value  xxxx

How do I send a parameter with the myCb call in doWork('a', 'b', myCb);? ( 'when you run the callback function , please run it according to value xxxx')

any help ?

p.s. I want to avoid any global flags solution

thanks.

• javascript

• may be duplicated stackoverflow./questions/1997531/… – mask8 Commented Jul 25, 2012 at 7:01
• @mask8 please search the term .bind in your link , I don't see it. so I assume it is not duplicate ( different solutions) – Royi Namir Commented Jul 25, 2012 at 7:02
• how about this one? stackoverflow./questions/3458553/… there are too much of this questions anyway – mask8 Commented Jul 25, 2012 at 7:07
• @mask8 Ok , Agree. ( didnt find it before though) ...:) – Royi Namir Commented Jul 25, 2012 at 7:07
• @RoyiNamir when that first question was written, ES5 had been approved less than a month prior. At that time, most browsers didn't support it, and most developers weren't familiar with it. The lack of .bind in the answers is definitely not suggestive that it is not a duplicate (and certainly not conclusive in any case). – apsillers Commented Jul 25, 2012 at 7:10

4 Answers 4

The mon solution is to create another function in place.

doWork('a', 'b', function () {
    myCb('xxxx');
});

You can also use a function that would abstract the currying away. JavaScript (ES5) even has one built-in – Function.prototype.bind. Mind you, the native bind will make your callback slow and has limited support in browsers (see the MDN page).

doWork('a', 'b', myCb.bind(null, 'xxxx'));

One of the solutions is to use .bind:

doWork('a', 'b', myCb.bind(null, 'xxx'));

Or you could use apply and arguments

console.log('calling doWork func...')
doWork('va', 'b', myCb);

function doWork(param1, param2, callback)
{
        console.log('in func')


        callback.apply(this,arguments);
}


function myCb(a)
{
        console.log('in callback... for value ' + a)
}

JSbin Example

console.log('calling doWork func...')
doWork (myCb, "a", "b");
function doWork (callback) {
console.log('in func')
callback (arguments[1], arguments[2]);
}
function myCb (param1, param2) {
console.log('in callback... for value ' + param1)
}

Hope this help you