setInterval(function(),time) change time on runtime

You're clearing the interval on the next line, so the first one wont work, as it gets cleared right away :

        timer = setInterval(come, 0);
        clearInterval(timer);
        timer = setInterval(come, 10000);

Also, as gdoron says, setting a interval of nothing isn't really valid, and not a really good idea either, use setTimeout instead, or just run the function outright if no delay is needed.

        come();
        clearInterval(timer);
        timer = setInterval(come, 10000);

You can't. You will need to use setTimeout, and call it repetitively:

var timer; // current timeout id to clear
function come(){ /* do something */};
var time; // dynamic interval

(function repeat() {
    come();
    timer = setTimeout(repeat, time);
})();

With this you can set a different "interval" to be applied each time the function repeat is executed. Yet, nothing changes if alter time during a timeout, you'd need to stop the timeout for that.

There is no way to directly change the interval at which a function fires. The best you can do is cancel an interval and set a new one with the same function and updated timer. Here's a possible way of doing it:

timer = {
    timers:{},
    inc:0,
    start:function(cb,gap) {
        var key = inc;
        inc++;
        timer.timers[key] = [setInterval(cb,gap),cb];
        return key;
    },
    stop:function(id) {
        if( !timer.timers[id]) return;
        clearInterval(timer.timers[id][0]);
        delete timer.timers[id];
    },
    change:function(id,newgap) {
        if( !timer.timers[id]) return;
        clearInterval(timer.timers[id][0]);
        setInterval(timer.timers[id][1],newgap);
    }
};

Usage:

var myTimer = timer.start(function() {....},1000);
// calls every second

timer.change(myTimer,5000);
// now calls every five seconds