Uncaught Error: Function "foo" not found!

[espruino-discuss]

Posted at 2016-07-16 by @MaBecker

what is wrong with my sample code - any comments ?

online with WEB IDE

var bla = {
  init : function() {
    console.log("bla.init");
    this.foo();
    this.bar();
  },
  foo : function() {
    console.log("bla.foo");
  },
  bar : function() {
    console.log("bla.bar");
  }
}

> bla.init();

/* output 

bla.init
bla.foo
bla.bar

*/

with E.on(): Uncaught Error.....

var bla = {
  init : function() {
    console.log("bla.init");
    this.foo();
    this.bar();
  },
  foo : function() {
    console.log("bla.foo");
  },
  bar : function() {
    console.log("bla.bar");
  }
}

E.on("init",bla.init)

setTimeout(save,2000);


/* output

bla.init
Uncaught Error: Function "foo" not found!
 at line 2 col 10
    this.foo();
         ^
in function called from system

*/

[gfwilliams]

Posted at 2016-07-16 by @gfwilliams

You need to use bla.init.bind(bla) or function(){bla.init()}, not just bla.init.

It's one of the 'gotchas' of JavaScript, and it's the same thing that happens for setInterval, setTimeout, or any callback.

Basically, when you call a function, like bla.init(), the this variable gets set up to bla. However, if you just pass bla.init, you're basically doing this:

var x = bla.init;
x();

In that case, x is just a function, that has no association with bla at all - so when you call it, this isn't set.

[espruino-discuss]

Posted at 2016-07-16 by @MaBecker

thanks !