Question

I am trying to make a text slide show with javascript, however in javascript the math floor function always returns the same random number. What is wrong with code below?

var randomnumber;
D=Array(7)
D[0]='Sunday!'
D[1]='Monday!'
D[2]='Tuesday!'
D[3]='Wednesday!'
D[4]='Thursday!'
D[5]='Friday!'
D[6]='Saturday!'

window.setTimeout("Tick()", 1000);    

function Tick() 
{
    document.write('<marquee><font size="+2">'+D[Math.floor(Math.random()*7)]+'</font></marquee>')    
}


</script>

Answer 1

Works fine. However, you must pass a reference to the function when using setTimeout and not a string. setTimeout uses an eval-like procedure when you pass it a string, making this method of usage unsafe.

function Tick() {...}

//pass a reference (no quotes)
window.setTimeout(Tick, 1000);​

---

setTimeout only fires once when the timeout is reached. If you want to do a constant, continuous Tick, then better use setInterval instead, which fires and “reloads” to fire again.

---

Here’s a modified version of the code to fit your description

//create the marquee and add to body 
var marquee = document.createElement('marquee');
document.body.appendChild(marquee);

function Tick() {
    //generate the random text
    var randomDay = D[Math.floor(Math.random() * 7)];

    //change the existing marquee text
    //textContent for compliant browsers
    //innerText for IE
    marquee.textContent = randomDay;
}

//tick every second
window.setInterval(Tick, 1000);​