Allow only numeric value in textbox using Javascript

Question

I want to allow only numeric values to be entered into the text and if user enters alphabetic character it should warn the user. Any suggestion for optimized and short javas

Answer 1

// Solution to enter only numeric value in text box

$('#num_of_emp').keyup(function () { 
    this.value = this.value.replace(/[^0-9.]/g,'');
});

for an input box such as :