Question

Any idea why I have the error Uncaught ReferenceError: hello is not defined ?

function hello() {
    console.log('hello ()');
    setTimeout("hello ()", 1000);
}
setTimeout("hello()", 1000);​

Here is a jsfiddle : http://jsfiddle.net/s9vLk/

Answer 1

The problem is that you are passing strings to setTimeout() which means code in the string will effectively be evaled and thus isn’t running in the scope you think it’s running in and so the hello() function isn’t found.

If you change the jsfiddle options on the left from “onload” to “no wrap” it works as is because then the function will be global rather than nested inside the onload handler, but a better option is to pass a function reference to setTimeout():

function hello() {
    console.log('hello ()');
    setTimeout(hello, 1000);
}
setTimeout(hello, 1000);

(Note: no parentheses after hello.)