CODEWITHSUNDEEP
javascript
wootscootinboogie
wootscootinboogie

Reputation: 8695

JavaScript: get to arguments object of callback

Fiddle here

I'm looking at making some very high level logic into helper functions for curiosity's sake. I would like to be able to execute a function with its parameters in the _if function without having to define something like _callback ahead of time? I feel like I'm missing something here.

var _if = function(predicate,callback){
    if(predicate){
        callback(); //callback(arguments) is not arguments for callback
    }
};
var text = 'some text';
_if(1 > 0,function(){
    console.log('hello world'); //hello world
});
_if(1 > 0,function(text){
    console.log(text); //undefined
});
//define callback for this situation
var _callback = function(x){
    console.log(x);
}
_if(1 > 0,function(){
    _callback(text); //some text
});

Upvotes: 0

Views: 82

Answers (2)

user669677
user669677

Reputation:

Not sure what you want, but maybe this helps:

You can call your function like this too:

_if(1 > 0,_callback.bind(null,text));  //null is the value of this

_if(1,function(text){
    console.log(text); //this way not undefined
}.bind(null,text));

1) This works because of the logic of JavaScript. In further versions you can use your version too if you use let text = 'some text'; - ref

2) null is the this value for the function, (more info here) but I think you can pass this too if you need to use it in the function (null will be automatically replaced in non-strict mode to the global object. That's why you can use window.colsole.log inside the function. - ref)

Upvotes: 1

Platinum Azure
Platinum Azure

Reputation: 46183

Why not just take the arguments to the callback function as extra parameters on _if?

var _if = function (predicate, callback, context) {
    if (predicate) {
        var callbackArgs = [].slice.call(arguments, 3);
        callback.apply(context || null, callbackArgs);
    }
};

// Usage:
_if(true, console.log, console, "text");

Upvotes: 1

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