Ascci stands for "American Standard Code for Information Interchange".
Check the KeyCode
We'll check each key event individually against each character, which the user enters in the textbox.
The ternary code var iKeyCode = (evt.which) ? evt.which : evt.keyCode works like the if…else condition.
However, you can also write the code in this way:
var iKeyCode; If (evt.which) iKeyCode = evt.which; Else iKeyCode = evt.keyCode; // Keywords are case sensitive.
The value in iKeyCode will be checked against a range of Ascii codes to make sure it’s a number (numeric value). The function will return true or false based on the entered value. No value will be displayed on the textbox control if the condition returns false.
When a user enters a value in the input box, the onkeypress event calls the isNumber() function (that I have written inside the <script> tag), along with the key press event. The function checks every key entered in the input box and returns true only if the entered values in a number, else it will return false. If it is false, the user won’t see any value in the box.
You should also try this
If you are a .net programmer, you can try a small assignment on your own. Use the Asp.Net textbox control instead of <input> box, and see if the function works as I have explained above.
<asp:TextBox ID="tbPh" runat="server"></asp:TextBox>
Thanks for reading. ☺