Html tags can be easily manipulated by using the DOM model of JavaScript. First, you get the DOM object of the input tag, so we can use the obtained inputTxta object to manipulate the tag, and you can use the API of the DOM object to add attributes. The code is as follows: First, create an attribute node Varattri = document. Create an attribute ("size"); Create a size attribute node, and then specify a specific length value for the size attribute. attri . value = " 10 "； (If you want to set the length of the text box to 10), then use the inputTxta object to add the attribute node to input xta. set attribute(attri) in the input tag; Done, hehe, I hope it will help you!