for

let str = "";

for (let i = 0; i < 9; i++) {
  str = str + i;
}

console.log(str);
// Expected output: "012345678"

for ([initialization]; [condition]; [final-expression])
   statement

for (var i = 0; i < 9; i++) {
  console.log(i);
  //  
}

var i = 0;
for (; i < 9; i++) {
  console.log(i);
  //  
}

for (var i = 0; ; i++) {
  console.log(i);
  if (i > 3) break;
  //  
}

var i = 0;

for (;;) {
  if (i > 3) break;
  console.log(i);
  i++;
}

function showOffsetPos(sId) {
  var nLeft = 0,
    nTop = 0;

  for (
    var oItNode = document.getElementById(sId) /* initialization */;
    oItNode /* condition */;
    nLeft += oItNode.offsetLeft,
      nTop += oItNode.offsetTop,
      oItNode = oItNode.offsetParent /* final-expression */
  ); /* semicolon */

  console.log(
    "Offset position of '" +
      sId +
      "' element:\n left: " +
      nLeft +
      "px;\n top: " +
      nTop +
      "px;",
  );
}

/* Example call: */

showOffsetPos("content");

// Output:
// "Offset position of "content" element:
// left: 0px;
// top: 153px;"