Some JavaScript techniques and functions that will be helpful in web development.

1. Toggling visibility of a table or a div or any other element:

function toggle(div_id) {
      var el = document.getElementById(div_id);
      if ( el.style.display == 'none' ) {  el.style.display = 'block';}
      else {el.style.display = 'none';}
}

2. Remove all child nodes of an element:

var Parent = document.getElementById('elementId');
while(Parent.hasChildNodes()) {
      Parent.removeChild(Parent.firstChild);
}

3. Validate radio group:

function checkradio(formNme,radioGroupName) {
      var radios=document[formNme].elements[radioGroupName];
      for(var i=0;i<radios.length;i++){
              if(radios[i].checked)
                      return true;
      }
      return false;
}

4. Sending an async request to server:

if (window.XMLHttpRequest) {
      xmlhttp = new XMLHttpRequest();
}
else {
      xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.open("POST", url, true);
xmlhttp.onreadystatechange = handleReadyStateChange;
xmlhttp.send(null);
function handleReadyStateChange()  {
      if (xmlhttp.readyState == 4) {
          ///--- Request completed
      }
}

5. To hide/disable scroll bar of a browser:

document.documentElement.style.overflow=document.body.style.overflow='hidden';
// To again enable scroll bar do as follows:
document.documentElement.style.overflow=document.body.style.overflow='auto';

6. Validate url using Regex:

function isValidURL(url){
      //var RegExp = /^(http:\/\/|https:\/\/|ftp:\/\/){1}([0-9A-Za-z]+\.)/;
      var RegExp = /^(http:\/\/){1}([0-9A-Za-z]+\.)/;
      if (RegExp.test(url)) {
               return true;
      }
      return false;
}

7. Swap table columns:

function swapColumns (table, colIndex1, colIndex2) {
      if (!colIndex1 < colIndex2){
            var t = colIndex1;
            colIndex1 = colIndex2;
            colIndex2 = t;
      }
      if (table && table.rows && table.insertBefore && colIndex1 != colIndex2) {
            for (var i = 0; i < table.rows.length; i++) {
                   var row = table.rows[i];
                   var cell1 = row.cells[colIndex1];
                   var cell2 = row.cells[colIndex2];
                   var siblingCell1 = row.cells[Number(colIndex1) + 1];
                   row.insertBefore(cell1, cell2);
                   row.insertBefore(cell2, siblingCell1);
            }
      }
}

8. Tab view:

Refer to this link.

9. Limiting textbox/textarea to number of characters:

Refer to this link.

• Java Script