Glow JS 0-01 Associative Array (broken)

/** Glow JS 0-01 Associative Array by Timothy Robert Keal **/

function array_dump_this(element,index,array){
    document.write('<font color="green">a[<font color="red">'+index+'</font>]="<font color="red">'+element+'</font>"</font><br>');
}

function array_dump(array){
    array.forEach(array_dump_this)
}
function addToArray(array) {
    array.push(prompt("Add items to array or 'q' to stop"));
    if (array[array.length-1] == 'q') {
        array.pop();
        array_dump(array);
    }
    else {
        addToArray(array);
    }
}
 addToArray([]);

 function addslashes(string) {
    return string.replace(/\\/g, '\\\\').
        replace(/\u0008/g, '\\b').
        replace(/\t/g, '\\t').
        replace(/\n/g, '\\n').
        replace(/\f/g, '\\f').
        replace(/\r/g, '\\r').
        replace(/'/g, '\\\'').
        replace(/"/g, '\\"');
}

function unicode_toHex(label=''){
    var ret='';
    var unicode='';
    for(var offset=0;offset<label.length;offset++){
        unicode=parseInt(label.charCodeAt(offset),10).toString(16);
        ret+=parseInt(unicode.length,10).toString(16)+unicode;
    }
    return ret;
}

 function array_op(mode='set',array='aa',arg_label='',arg_value=1){
    var label=unicode_toHex(arg_label);
    var addr=array;
    var addr_last='';
    var i=0;
    for(var offset=0;offset<label.length;offset++){
        addr_last=addr;
        addr+='['+parseInt(label.substring(offset,offset),16)+']';
        if(eval(addr+'===undefined')
            for(i=0;i<=16;i++)
                eval(addr_last+'.push(\'\');');
    }
    if(eval(addr+'[16]===undefined')
        for(i=0;i<=16;i++)
            eval(addr+'.push(\'\');');
    addr+='[16]';
    switch(mode){
        case 'get':
            return eval(addr);
            break;
        case 'set':
            return eval(addr+'=\''+addslashes(arg_value)+'\'');
            break;
        case 'inc':
            return eval(addr+'+='+arg_value);
            break;
        case 'dec':
            return eval(addr+'-='+arg_value);
        case 'append':
            return eval(addr+'+=\''+addslashes(arg_value)+'\'');
            break;
        case 'seek':
            return addr;
            break;
        default
            return null;
    }
}