Question

This is the code snippet of everything I think I need to describe this problem. I am trying to have a continuous action go off when the mousedown is activated, but am getting the error:

Uncaught ReferenceError: e is not defined
(anonymous function)

I’m pretty sure this error is stemming from the beginAction function where I have findClick(e) in quotes, somehow I don’t think e is getting passed correctly here:

function Cell(row, column) {
    this.row = row;
    this.column = column;
    }

function foo(bar) {
    //do stuff here
    gCanvas.addEventListener("mousedown", beginAction, false);
    document.addEventListener("mouseup", endAction, false);
    }

function beginAction(e) {
    findClick(e);
    var findClick_timeout = setInterval("findClick(e)", 50);
    }

function endAction(e) {
    if (typeof(findClick_timeout) != "undefined"){ clearTimeout(findClick_timeout);}
    }
    
function getCursorPosition(e) {
    //finds the cell position here... works
    var cell = new Cell(Math.floor(y/cellSize), Math.floor(x/cellSize));
    return cell;
    }

function findClick(e) { 
    var cell = getCursorPosition(e);
    //do stuff with the cell!!!!!!
    }

Answer 1

Timer strings are converted to functions in the global scope. That’s why you shouldn’t use them:

var findClick_timeout = setInterval(function() { findClick(e); }, 50);

This way, that little anonymous function will have access to the “e” from the “beginAction” function it was created in. When you pass just a string, however, the runtime evaluates that in the global scope, and there’s no “e” out there.

In newer browsers, there’s a function called “bind” that you can use for this:

var findClick_timeout = setInterval(findClick.bind(this, e), 50);

It’s just a tool for doing essentially what the anonymous function does.