Question

I’m working on a dynamic validation system. For some reason, shift() on the args array mainfunc passes to validateNumber does not act properly. Here’s the code with output in comments next to alert boxes:

function mainfunc (func){
    //this calls the function validateNumber and passes args to it.
    this[func].apply(this, Array.prototype.slice.call(arguments, 1));
}

function validateNumber(args) {
    alert(args); //this functions normally. for example, displays fish,3,5
    var text = args.shift; //would expect this to return 'fish', right?
    alert(text); //instead of 'fish' alerts 'function shift() { [native code] }'. This is the problem.
    var minimum = args.shift;
    var maximum = args.shift;
    return text;
}

validationArgs = classList[i].split('-');
    functionName = validationArgs.shift();
    validationArgs.unshift($(this).val());
    mainfunc(functionName, validationArgs); //calls mainfunc which calls the function

I’m stumped as to why this behaves this way. Note: I cribbed mainfunc from this StackOverflow answer: Calling dynamic function with dynamic parameters in Javascript

Edit: Oh, my goodness. I am an idiot. I even use shift() correctly in the title of the question! Thanks all.

Answer 1

This:

var text = args.shift;

is not a method call, you want:

var text = args.shift();

All your original does is assigns the shift method from args to text, hence your:

function shift() { [native code] }

output in your alert. Doing a args.shift won’t have any effect on args so these two:

var minimum = args.shift;
var maximum = args.shift;

just give you two more reference’s to args.shift without changing args at all.