Inject additional parameters into a JavaScript callback function

Question

I have spend a lot of time trying to find a title that explain my question, but not easy. Feel free to suggest.

Code is as follow: I am creating annotation for my chart using google visualisation. The annotation column uses a custom function. This is allowed by google, and the function will received 2 parameters: dt and row. The question is: what should (dt, row, i) in the below be so that I get the default dt, row that the function normally receives and my additional parameter i?

view = new google.visualization.DataView(chartData);
var arr = [0];

for (var i = 1; i < chartData.getNumberOfColumns() ; i++) 
{
    arr.push(i);
    arr.push({role: "annotation", type: "string", calc: (function (dt, row,i)  {
        if (typeof (dt.getValue(row,i)) == "number" && dt.getValue(row,i) == 0) 
        {
            return ""; 
        }
        else 
        { 
            return dt.getValue(row, i).toString; 
        }
    })(dt, row, i)
});
}

view.setColumns(arr);
chartData = view.toDataTable();

A title that I feel describes better your question would be; Inject additional parameters into a JavaScript callback function — ppoliani
– ppoliani, Commented Jan 31, 2014 at 16:04

ppoliani · Accepted Answer · 2014-01-31 13:04:17Z

2

I don't know if i got it right, but you can probably use a higher order function for that:

var createCalc = function(i){
    return function(dt, row){
        if (typeof (dt.getValue(row,i)) == "number" && evs == 0) { return ""; }
        else { return dt.getValue(row, i).toString; }
    };
}

...
arr.push({role: "annotation", type: "string", calc: createCalc(i)});

answered Jan 31, 2014 at 13:04

ppoliani

4,9164 gold badges38 silver badges65 bronze badges

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

Comments

schnill · Accepted Answer · 2014-02-02 05:03:23Z

1

lets say you have a function createCalc which receives two parameters dt and row from the callback and you want to add your additional parameter i to it. Create a function,

function createCalc(i, dt, row) {
  //functin code
}

and pass it as,

arr.push({role: "annotation", type: "string", calc: createCalc.bind(null, i)});

bind will return a new function adding parameters to it. first argument, i have passed is null, it is actually will be assigned to this variable, pass appropriate value if u use this in your function.

answered Feb 2, 2014 at 5:03

schnill

9551 gold badge5 silver badges13 bronze badges

Collectives™ on Stack Overflow

Inject additional parameters into a JavaScript callback function

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related