Arguments to JavaScript Anonymous Function

Question

for (var i = 0; i < somearray.length; i++)
{
    myclass.foo({\'arg1\':somearray[i][0]}, function()
    {
        console.log(somearray[i][0]);
    });
}

Answer 1

The i in the anonymous function captures the variable i, not its value. By the end of the loop, i is equal to somearray.length, so when you invoke the function it tries to access an non-existing element array.

You can fix this by making a function-constructing function that captures the variable's value:

function makeFunc(j) { return function() { console.log(somearray[j][0]); } }

for (var i = 0; i < somearray.length; i++)
{
    myclass.foo({'arg1':somearray[i][0]}, makeFunc(i));
}

makeFunc's argument could have been named i, but I called it j to show that it's a different variable than the one used in the loop.