如何使用javascript在循环中每行添加一个新字符？

Question

Not sure if the title makes sense, but I'm trying to figure out how to make a loop in javascript that would add a character each time it loops. Say for example I want to add a "0" for each line, so the output would look like this...

0

00

000

0000

This is what I have so far

var count;
document.write("Starting Loop" + "<br />");
for(count = 0; count < 4; count++){
  document.write("0");
  document.write("<br />");
}
document.write("Loop stopped!");

Answer 1

You really shouldn't use document.write , but here's a solution with the same structure:

var count;
var str = '0';
document.write("Starting Loop" + "<br />");
for(count = 0; count < 4; count++, str += '0'){
  document.write(str);
  document.write("<br />");
}
document.write("Loop stopped!");

JSFiddle

Answer 2

If the character you want added does not change then I suggest something like:

   var count;
   var s = "0";
   var endChar = "0"
   document.write("Starting Loop" + "<br />");
   for(count = 0; count < 4; count++){
       document.write(s);
       document.write("<br />");
       s += endChar;
   }
   document.write("Loop stopped!");

Answer 3

So build a string and keep adding to it

var s = "0";
console.log(s);
for(var count = 1; count < 4; count++){
    s = s + "0";
    console.log(s);
}