在php javascript中找到没有onload函数的动态文本框值的count char

I am having a dynamic text box. I need this text box char count but only one without page load function. Any help?

How about:

<input type="text" onkeyup="count(this);" />

function count(input) {
    console.log(input.value.length);
}

If you want something else, please elaborate more about what it is you want, what you already have, errors you might be facing and code.