实现此序列的最快方法？

Question

I'm trying to create a simple algorithm that builds an array with a dynamic length.

Then, it will, one by one, replace an item, and then two, then three and so on until the only items left are the first and last.

like this:

12345

1*345 // it never touches the first
12*45
123*5 // it doesn't ever touch the last item

1**45
12**5

1***5 // done, nowhere else to go

I put together a simple demo to show what I'm trying to do.

var length = 6,
    array = [],
    log = document.getElementById("log"),
    edited,
    j,
    i;

for (i = 1; i <= length; i++) {
    array.push(i);
}

log.innerHTML += array.join(" ") + "<br><br>";

for (i = 1; i < (length - 1); i++) {
    edited = array.concat();
    for (j = i; j < (length - 1); j++) {
        edited[j] = "*";
        log.innerHTML += edited.join(" ") + "<br>";
    }
    log.innerHTML += "<br>";
}

Fiddle

It works fine, the only problem is it's out of order. Right now it seems to only iterate by number of asterisks, then by index. I need it to do the opposite.

// it does this
12345

1*345
1**45
1***5

12*45
12**5

123*5 // out of order

If someone could help that would be great because I am really at a loss!

Answer 1

This should get it done.

var a = 6, // array length
    b = [], // array
    log = document.getElementById("log"),
    c,
    d,
    e;

for (c = 1; c <= a; c++) {
    b.push(c);
}

log.innerHTML += b.join(" ") + "<br><br>";

//the size of the asterisk chunk
for(i = 1; i < b.length - 1; i ++)
{
    //position to start asterisk chunk
    for(j = 1; j < b.length - i; j ++)
    {
        var tempArr = b.concat();

        //the position inside of the asterisk chunk
        for(k = 0; k < i; k ++)
        {
            tempArr[k + j] = "*";
        }

        log.innerHTML += tempArr.join(" ") + "<br>";
    }
}

JSFiddle

Answer 2

This seems to work well:

 str = "1234567" len = str.length; for(var stars = 1; stars < len - 1; stars++) { for(var pos = 1; pos < len - stars; pos++) { var s = str.substr(0, pos) + new Array(stars + 1).join("*") + str.substr(pos + stars); document.write(s + "<br>"); } }