Edit Table Cell in Place

Let's create a function that will get a reference to a table cell as a parameter, and make the table cell editable. In other words, create Edit In Place. Our function will be very simple, and use only standard DOM methods. It will be called by clicking on the table cell.

 function makeEditable(el){
 }

The el variable will hold a reference to a table cell. Normally, a table cell will have one childNode - the text element. First we check whether this is the first click on the table cell:

  if(el.firstChild.nodeName !="INPUT"){
  }

If it is so, we create an input element:

 var input = document.createElement("INPUT");

Assign the value of the cell text to the input element and set different background:

 input.value = el.firstChild.nodeValue;
   input.style.background = "rgb(255,244,255)";

Turn autocomplete off to avoid the 'Permission denied to set property XULElement.selectedIndex' error in Firefox.

 input.setAttribute('autocomplete','off');

Replace the text with the input element we just created and set focus on it:

  el.replaceChild(input, el.firstChild);
  el.firstChild.select();
  el.firstChild.focus();

To turn the input element back into text, we'll do the reverse procedure - create a text node, and replace the input element with text:

 var text= document.createTextNode(el.firstChild.value);
 el.replaceChild(text, el.firstChild);

The function will called from a cell element as follows:

onclick=makeEditable; 

Once a user turned the input back into text, you could apply various Ajax techniques to save the modified text on the server.

Here is the full function listing:

function makeEditable(){
 var el = this;
 if(el.firstChild.nodeName !="INPUT"){
   var input = document.createElement("input");
    input.value = el.firstChild.nodeValue;
    input.setAttribute('autocomplete','off');
    input.style.background = "rgb(255,244,255)";
    el.replaceChild(input, el.firstChild);
    el.firstChild.select();
    el.firstChild.focus();
   }
   else{
    var text= document.createTextNode(el.firstChild.value);
  el.replaceChild(text, el.firstChild);
   }
 }

When the makeEditable function is called from a table cell, the keyword this in the function refers to the table cell element.

Unobtrusive JavaScript

There is a way to attach a function to the onclick event in each table cell without having to write inline code. Here is how to do it:

function addEventHandlers() {
  //the table should have an id
  var table = document.getElementById('example');
  var tds = table.getElementsByTagName('td');
  for(var i=0; i< tds.length; i++){
   //no brackets after the function name
   tds[i].onclick = makeEditable;
   tds[i].title = 'Click to edit';
  }
}

The last step is to make sure this function is called after a page has loaded:

window.onload = addEventHandlers;

-->

Related posts:

How to Change HTML Table Cell Value

Hide Columns in a Table

Delete Table Rows

To delete selected rows from a table, obviously, we need to add checkboxes to every table row. When a checkbox is checked, it means that that particular row will be deleted. Also, we need some method by which we could identify a selected row. The value attribute of a checkbox is a very good candidate for that. It will equal a row index. As you know, row indices start at 0, so the value of first row checkbox will equal 0, the value of the second row checkbox will equal 1, and so on.
Now, we can write a function to be called from the Delete button:
First, we get a reference to the table:

var table = document.getElementById("myTable");

Then, we get a reference to the array of checkboxes in the table:

var checks = table.getElementsByTagName("input");

Normally, this array will contain all the inputs in the table, and we would have to use the type property to get a reference to desired elements. However, if we are sure that there are no other inputs in the table other than the checkboxes, we can skip this check.
Now, we iterate through all the checkboxes. If the checked property is true, we obtain the index of a row which is contained in the checkbox value property, and delete this row. Also, we have iterate backwards, because otherwise removing a row changes the subsequent row index by -1. Iterating backwards preserves our indices.

for(var i= checks.length-1; i>=0; i --){
 if(checks[i].checked){
  var indx =  checks[i].value;
  table.deleteRow(indx);
 }
}

The next step resets the values of the checkboxes to make sure that they correspond to the new row indices.

var checks = table.getElementsByTagName("input");
for(var i= 0; i < checks.length; i++){
 checks[i].value=i;
}

Here is the complete function listing :

function deleteRows(){
 var table = document.getElementById("myTable");
 var checks = table.getElementsByTagName("input");

 for(var i= checks.length-1; i>=0; i --){
  if(checks[i].checked){
   var indx =  checks[i].value;
   table.deleteRow(indx);
  }
 }
 var checks = table.getElementsByTagName("input");
 for(var i= 0; i < checks.length; i++){
  checks[i].value=i;
 }
}

Hide Columns in Table

To hide or show table columns, first we get a reference to the table

var table = document.getElementsByTagName("table")[0];

Then we get a reference to the rows collection:

var rows = table.rows;

Let's say we want to hide the first column in the table. We iterate through each row and set the display property of the first element in the cells collection to none.

for(var i=0; i< rows.length; i++){
 rows[i].cells[0].style.display='none';
}

To show a particular column, we would set the display property to blank.

for(var i=0; i< rows.length; i++){
 rows[i].cells[0].style.display='';
}

DOM Hyperlinks

First, here is the code. Then I'll explain it:

 var link  = document.createElement("A");
 link.href = "http://www.google.com";
 var atext = document.createTextNode("Google");
 link.appendChild(atext);
 oElement.appendChild(link);

First, you create an HTMLAnchorElement using a DOM method createElement(tagName).

var link  = document.createElement("A");

Then, you set the href property of the HTMLAnchorElement:

link.href = "http://www.google.com";

Next, you create a text node that will hold the clickable text:

var atext = document.createTextNode("Google");

Then, append the text node to the HTMLAnchorElement:

link.appendChild(atext);

Now, you can append the link element to another element on the page:

oElement.appendChild(link);

oElement holds a reference to an HTML element on the page that will be a parent of the newly created hyperlink.
Here is the same code presented as a function that accepts 3 parameters: parent element, url and link text:

function createLink(parent, url, linkText){
 var link  = document.createElement("A");
 link.href = url;
 var atext = document.createTextNode(linkText);
 link.appendChild(atext);
 parent.appendChild(link);
}

Check Radio Button State

If you have radio buttons and one of the buttons is checked by default, you may need to check if the buttons state has been changed, and only then proceed with form submission. Suppose you have a group of radio buttons named 'cities':

<input type="radio" name="cities" value="Paris"> Paris<br>
<input type="radio" name="cities" value="London" checked> London<br>
<input type="radio" name="cities" value="Berlin">Berlin<br>

Here is a JavaScript function that will return true if a radio button value has been changed, and false if not. We assumed that the form name is frm1.

function checkRadioButtons(){
 var rr = document.frm1.cities;
 var len = rr.length;
 while(len-->0){
  if(rr[len].checked !=rr[len].defaultChecked)
   return true;
 }
 return false;
}

Radio buttons and checkboxes have a defaultChecked property which reflects the initial state of an element's checked attribute. The code loops through each radio button and checks whether the current checked property is equal to the defaultChecked property of an element, in which case it means that the element state has been changed.
This function is called on form submit as follows: 'return checkRadioButtons()'. If the function returns true, the form submission takes place. If the function returns false, nothing happens.

Highlight All Links on a Web Page

The following JavaScript code will highlight each html link on a web page when you hover your mouse over it.

Get an array of all html links on a web page:

 var aa = document.getElementsByTagName('a');

Loop through the array and assign anonymous functions on mouseover and mouseout events:

    for(var i=0; i<aa.length; i++){
        aa[i].onmouseover = function () {this.style.backgroundColor='#cc0000'}
        aa[i].onmouseout = function () {this.style.backgroundColor='#ffffff'}
    }

The above code works and is fine. However, there is a better and shorter solution that does not require JavaScript and uses CSS. Here is how you do it. In your CSS file, include the following declaration :

 a:hover {background-color:#cc0000;}