Validating special character using Javascript

Javascript Code:

function specialcharecter()

{

var iChars = "!`@#$%^&*()+=-[]\\\';,./{}|\":<>?~_";

var data = document.getElementById("txtCallSign").value;

for (var i = 0; i < data.length; i++)

{

if (iChars.indexOf(data.charAt(i)) != -1)

{

alert ("Your string has special characters. \nThese are not allowed.");

document.getElementById("txtCallSign").value = "";

return false;

}

}

}

Note: ‘txtCallSign’ is the Id of the textbox.