Recursive Call in controller Lightning

Question

I want to make recursive call in js controller on my lightning component.. Following is my js controller but I am getting an error as

'callback' must be a valid Function

check : function(component, event, helper) {
    var str = component.get('v.message');
    if(str == null){
        str = '';
    }
    $A.getCallback(helper.check(component,str),1200);
}

ControllerHelper Code :

check : function(cmp,a) {
    var msg = 'Welcome to Dairy Startup';
    if(a.length < msg.length){
        a = msg.substring(0,a.length + 1);
        cmp.set('v.message',a);
    }
}

How Can I make recursive call to helper method?

Answer 1

You're actually calling the function, but instead what you want to do is bind it to get a function. That looks like this:

$A.getCallback(helper.check.bind(helper,component,str));

Where the first parameter is the "this" variable (the helper), and the parameters thereafter are function parameters.

You can read more about binding over on MDN.

You also are presumably trying to create a delay, so you need to use setTimeout:

setTimeout($A.getCallback(helper.check.bind(helper,component,str)), 1200);