Problems with self calling object function

[Bob90]

If anyone can help with this I woulg be grateful.
I think this is the offending line:

setTimeout("this.walk()",5000)

Here is the full code:

<script>
function person()
	{
	this.walk = walk;
	this.move=0;
	this.position = 0;
	}
	
function walk()
	{
	this.position += 2;
	if(this.position<= 10)
		{
		alert("Walking")
		setTimeout("this.walk()",5000)
		}
	else
		{
		alert("Finished walking")
		}
	}

James = new person();
James.walk();
</script>

Something wrong with calling the same object function from within itself?

Cheers

[Twey]

<script>

The type attribute is required.

function person()
...
James = new person();

The convention for constructor functions is that they start with a capital, and the convention for variables is that they don't. In English we use capitals for proper nouns; in Javascript, we don't.

this.walk = walk;

This is what prototypes are for.

setTimeout("this.walk()",5000)

If you pass a string to setTimeout() (which is bad practice), it will be evaluated in the global scope, so this isn't defined. Instead, you can store a reference to the current object in a variable and use a closure:

<script type="text/javascript">
  function Person() {
    this.move = 
      this.position =
      0;
  }
        
  Person.prototype.walk = function() {
    this.position += 2;
    if(this.position <=  10) {
      alert("Walking");
      var me = this;
      setTimeout(function() { me.walk(); }, 5000);
    } else
      alert("Finished walking")
  };

  var james = new Person();
  james.walk();
</script>

[Bob90]

Hey Twey,

Thanks for the help.
I have never used anything but strings in setIntervals and setTimeouts :S, so that is a real education.

One little thing: you say it is evaluated in the global scope, yet you initiate the variable 'me' with var, making it local. Or am I confused?

Thanks again.

[Twey]

One little thing: you say it is evaluated in the global scope, yet you initiate the variable 'me' with var, making it local.

A closure is able to access the local variables in the scope in which it was created no matter where it's called. That's the defining feature of a closure. If we made "me" global, it could lead to race conditions.