A JS fix only allowed to enter numbers and letters

A JS fix the input box allows the user to enter only the number and letter type of content, the object is input box, of course, other objects, but the input box is very high frequency. A code, do not believe it? Let's look at the code below:

<class maxLength size name   ID= "username"  onKeyUp= "Value=value.replace (/[\w]/g, ')"  ></INPUT>

After you add the onkeyup function to the input text box, you will find that when you enter other types of characters except numbers and letters, the cursor automatically deletes the characters you enter, unless you enter a number or a letter. Practical, huh?

A JS fix only allowed to enter numbers and letters