Input Field onchange not working

Question

I have an input field in apex given below

<apex:inputField value="{!paymentDetails.Amount__c}" onChange="enableLppAmount(this)" required="true" />

Also I have a simple input box

<input type="number" id="lppAmount" disabled="true"/>

I have the following javascript

function enableLppAmount(input){
    if(input.value.length > 0){
    document.getElementById("lppAmount").disabled=false;
    }
    else {
     document.getElementById("lppAmount").disabled=false;
    }
    }

Now When i enter any number in the apex input it is not enabling the html input. Basically the function is not being called. I want that when someone enters value in the apex input the simple input should be enabled and if no value then disabled. thanks for any help.

Answer 1

you have forget to apply semi coloun after calling javascript method

<apex:inputField value="{!paymentDetails.Amount__c}" onChange="enableLppAmount(this);" required="true" />

also script must be in

<script> function enableLppAmount(input){
    if(input.value.length > 0){
    alert(hi);
    document.getElementById("lppAmount").disabled=false;
    }
    else {
     document.getElementById("lppAmount").disabled=false;
    }
    }
</script>

tags

Answer 2

Here are the reasons why code was not working:

alert(hi);

This statement will treat 'hi' as a javascript variable and will try to find out 'hi' variable. As there is no 'hi' variable in code it will throw error and rest of the function will not work properly. Another problem:

 document.getElementById("lppAmount").disabled=false;

Same statement is written in if and else blocks. So Same behavior will be experienced for every change in input value.