在背后的代码中通过函数调用传递客户端ID时，无法通过aspx页面上的javascript函数访问字段的值（页面加载）

Question

I have a javascript function as follows

function textCounter(field, rem, maxlimit) {
        if (field.value.length > maxlimit)
            field.value = field.value.substring(0, maxlimit);
        else
            rem.value = maxlimit - field.value.length;
    }

I am trying to call it from code behind by passing clien ID's

ClientScript.RegisterStartupScript(this.GetType(), "myScript", "textCounter('" + txtRemark.ClientID + "','" + txtRemarksRem.ClientID + "', '2000')", true);

But I am unable to get the values of the associated fields. I am getting null value for "field.value.length"

Let me know the issue.

Answer 1

You are passing only client Ids for the controls, but not the control, you should first get those control to work.

for that you should change your code as

function textCounter(field, rem, maxlimit) {

    var fieldCtrl = document.getElementById(field);
    var remCtrl = document.getElementById(rem);

    if (fieldCtrl.value.length > maxlimit)
        fieldCtrl.value = fieldCtrl.value.substring(0, maxlimit);
    else
        remCtrl.value = maxlimit - fieldCtrl.value.length;

}