javascript - Inject variable into callback function scope - Stack Overflow

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Is this possible to add variable to callback scope? What I want to achieve is:

...
Foo.prototype.bar = function(fn) {
    var baz = "baz!";
    fn.call(this);
}
...

Foo.bar(function() {
    console.log(baz) // gives "baz!"
});

I know I can pass baz variable as an argument or this but I'm interested in something like above.

Is this possible to add variable to callback scope? What I want to achieve is:

...
Foo.prototype.bar = function(fn) {
    var baz = "baz!";
    fn.call(this);
}
...

Foo.bar(function() {
    console.log(baz) // gives "baz!"
});

I know I can pass baz variable as an argument or this but I'm interested in something like above.

• javascript
• scope
• closures

Share Improve this question Follow asked Dec 24, 2011 at 21:24 jesperjesper 88988 silver badges2121 bronze badges 1

• You probably mean (new Foo).bar, since it's a property of instances, not of the constructor. – pimvdb Commented Dec 24, 2011 at 22:50

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 4

No, it's not possible. The only ways are the ones you pointed out: as an argument or in this.

What about doing it this way:

var Foo = function(){}
Foo.prototype.handle = function(fn) {
    var baz = "baz !";
    eval('(' + fn.toString() + ')();');
}

var foo = new Foo;
foo.handle(function (){
    console.log(baz);
});

Is this possible to add variable to callback scope? What I want to achieve is:

...
Foo.prototype.bar = function(fn) {
    var baz = "baz!";
    fn.call(this);
}
...

Foo.bar(function() {
    console.log(baz) // gives "baz!"
});

I know I can pass baz variable as an argument or this but I'm interested in something like above.

Is this possible to add variable to callback scope? What I want to achieve is:

...
Foo.prototype.bar = function(fn) {
    var baz = "baz!";
    fn.call(this);
}
...

Foo.bar(function() {
    console.log(baz) // gives "baz!"
});

I know I can pass baz variable as an argument or this but I'm interested in something like above.

• javascript
• scope
• closures

Share Improve this question Follow asked Dec 24, 2011 at 21:24 jesperjesper 88988 silver badges2121 bronze badges 1

• You probably mean (new Foo).bar, since it's a property of instances, not of the constructor. – pimvdb Commented Dec 24, 2011 at 22:50

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 4

No, it's not possible. The only ways are the ones you pointed out: as an argument or in this.

What about doing it this way:

var Foo = function(){}
Foo.prototype.handle = function(fn) {
    var baz = "baz !";
    eval('(' + fn.toString() + ')();');
}

var foo = new Foo;
foo.handle(function (){
    console.log(baz);
});

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