Adds support for custom starting point

[Starefossen]

This fork adds support for custom starting point.

introjs().start(2); // 2 refers to the data-step="2"

[afshinm]

This pull request is really nice but I think it needs a little changes.
We should have a separate method like goToStep that has an step:integer parameter. This method set the current step of introduction, so we're able to go to specific step in the introduction.

Let me know what you think.

[Starefossen]

Well, maybe in addition to the .start( integer step ). I mean, how would you trigger the .goToStep( integer step ) function while introjs is running? The user isn't supposed to click on any buttons or anything because the rest of the screen is grayed out.

I'm using this option to start introjs at a given step using small ? at various places on my page; assuming that if the user has reached this point all the earlier steps has been completed.

[afshinm]

Ok ok, (you know that) we have chainable structure in introJs so you're able to do something like:

introJs().start().oncomplete(function(){ 
    //blah blah   
});

And I think it's better to do introJs().start().goToStep(2) instead of introJs().start(2) though I think we can have an parameter for start method that calls goToStep function then.
It's better to have separate small functions, it's a best practice.

[Starefossen]

I did not think of that @afshinm, good point. I very much like your proposed setup!

[afshinm]

Thanks to you @Starefossen.

[dfjones1981]

Doesn't the start() function display the first step though? If we called start() then gotostep(2) wouldn't that display the first step and then quickly switch to step 2?

[afshinm]

@dfjones1981 Yeah, correct. I know it's not a proper behavior. I think it's better to have a paramater for start function that calls goToStep first. Then we have this sequence of function calls:

start ==> goToStep (this function sets the _currentStep to given paramter) ==> _introForElement

So it starts the introduction from the given step.

[dfjones1981]

Sounds good. Also, as long as the start() method is called last you could still make use of the method chaining pattern, for example:

introJs().goToStep(2).start()

[afshinm]

@dfjones1981 Yeah yeah 👍

[saiful]

I think it can be added a plugin like using jquery.cookies. what do you think?

[afshinm]

@saiful Another discussion? It's better to have discussions in the project Google Group.

[afshinm]

@Starefossen And also this pull request, I think it's really a good feature to be added for v0.3.0 of IntroJs

[afshinm]

Manually added, thanks @Starefossen :)