Textbox should not contain special character using JavaScript

Call Javascript function on “onkeyup” event of TextBox

function valid(field) {
var txt = document.getElementById(‘TextBox1′).value;
var iChars = “!@$%^&*()+=-[]\\\’;,./{}|\”:?~_”;
for (var i = 0; i < txt.length; i++) {
if (iChars.indexOf(txt.charAt(i)) != -1) {
alert(“Your string has special characters. \nThese are not allowed.”);
document.getElementById(‘TextBox1′).value = txt.substring(0, txt.length – 1);
return false;
    }
  }
}

function isSpclChar(){
var iChars = "!@#$%^&*()+=-[]\\\';,./{}|\":?";
for (var i = 0; i < document.qfrm.q.value.length; i++) {
    if (iChars.indexOf(document.qfrm.q.value.charAt(i)) != -1) {
    alert ("The box has special characters. \nThese are not allowed.\n");
    return false;
        }
    }
}