Question

I was trying to define an array (including other arrays as values) in a single javascript statement, that I can loop through to validate a form on submission.

The function I wrote to (try to) create inline arrays follows:

function arr(){
    var inc;
    var tempa = new Array(Math.round(arguments.length/2));
    for(inc=0; inc<arguments.length; inc=inc+2) {
        tempa[arguments[inc]]=arguments[inc+1];
    }
    return tempa;
}

This is called three times here to assign an array:

window.validArr = arr(
    'f-county',arr('maxlen',10, 'minlen',1),
    'f-postcode',arr('maxlen',8, 'minlen',6)
);

However in the javascript debugger the variable is empty, and the arr() function is not returning anything. Does anyone know why my expectations on what this code should do are incorrect?

(I have worked out how to create the array without this function, but I’m curious why this code doesn’t work (I thought I understood javascript better than this).)

Answer 1

Well from what your code does, you’re not really making arrays. In JavaScript, the thing that makes arrays special is the management of the numerically indexed properties. Otherwise they’re just objects, so they can have other properties too, but if you’re not using arrays as arrays you might as well just use objects:

function arr(){
    var inc;
    var tempa = {};
    for(inc=0; inc<arguments.length; inc=inc+2) {
        tempa[arguments[inc]]=arguments[inc+1];
    }
    return tempa;
}

What you’re seeing from the debugger is the result of it attempting to show you your array as a real array should be shown: that is, its numerically indexed properties. If you call your “arr()” function as is and then look at (from your example) the “f-county” property of the result, you’ll see something there.

Also, if you do find yourself wanting a real array, there’s absolutely no point in initializing them to a particular size. Just create a new array with []:

    var tempa = [];