How to Call a JS function using OnClick event

问题

I am trying to call my JS function that I added in the header. Please find below code that shows my problem scenario. Note: I don't have access to the body in my application. Everytime I click on the element with id="Save" it only calls f1() but not fun(). How can I make it call even my fun()? Please help.

  <!DOCTYPE html>
  <html>
  <head>

  <script>

   document.getElementById("Save").onclick = function fun()
    {
     alert("hello");
     //validation code to see State field is mandatory.  
    }   

    function f1()
    {
       alert("f1 called");
       //form validation that recalls the page showing with supplied inputs.    
    }

  </script>
  </head>
  <body>
  <form name="form1" id="form1" method="post">
            State: 
            <select id="state ID">
               <option></option>
               <option value="ap">ap</option>
               <option value="bp">bp</option>
            </select>
   </form>

   <table><tr><td id="Save" onclick="f1()">click</td></tr></table>

   </body>
   </html>

回答1:

You are attempting to attach an event listener function before the element is loaded. Place fun() inside an onload event listener function. Call f1() within this function, as the onclick attribute will be ignored.

function f1() {
    alert("f1 called");
    //form validation that recalls the page showing with supplied inputs.    
}
window.onload = function() {
    document.getElementById("Save").onclick = function fun() {
        alert("hello");
        f1();
        //validation code to see State field is mandatory.  
    }
}

JSFiddle

回答2:

You could use addEventListener to add as many listeners as you want.

  document.getElementById("Save").addEventListener('click',function ()
    {
     alert("hello");
     //validation code to see State field is mandatory.  
    }  );

Also add script tag after the element to make sure Save element is loaded at the time when script runs

Rather than moving script tag you could call it when dom is loaded. Then you should place your code inside the

document.addEventListener('DOMContentLoaded', function() {
    document.getElementById("Save").addEventListener('click',function ()
    {
     alert("hello");
     //validation code to see State field is mandatory.  
    }  ); 
});

example

回答3:

I removed your document.getElementById("Save").onclick = before your functions, because it's an event already being called on your button. I also had to call the two functions separately by the onclick event.

     <!DOCTYPE html>
      <html>
      <head>
      <script>
       function fun()
        {
         alert("hello");
         //validation code to see State field is mandatory.  
        }   
        function f1()
        {
          alert("f1 called");
           //form validation that recalls the page showing with supplied inputs.    
        }
      </script>
      </head>
      <body>
      <form name="form1" id="form1" method="post">
                State: 
                <select id="state ID">
                   <option></option>
                   <option value="ap">ap</option>
                   <option value="bp">bp</option>
                </select>
       </form>

       <table><tr><td id="Save" onclick="f1(); fun();">click</td></tr></table>

   </body>
   </html>

回答4:

Inline code takes higher precedence than the other ones. To call your other function func () call it from the f1 ().

Inside your function, add a line,

function fun () {
// Your code here
}

function f1()
    {
       alert("f1 called");
       //form validation that recalls the page showing with supplied inputs.    

fun ();

    }

Rewriting your whole code,

 <!DOCTYPE html>
    <html>
      <head>

      <script>

       function fun()
        {
         alert("hello");
         //validation code to see State field is mandatory.  
        }   

        function f1()
        {
           alert("f1 called");
           //form validation that recalls the page showing with supplied inputs.   
           fun (); 
        }

      </script>
      </head>
      <body>
       <form name="form1" id="form1" method="post">

         State: <select id="state ID">
                   <option></option>
                   <option value="ap">ap</option>
                   <option value="bp">bp</option>
                </select>
       </form>
       <table><tr><td id="Save" onclick="f1()">click</td></tr></table>

      </body>
</html>

回答5:

Using onclick attribute or apply a function to your JS onclick properties will erase your onclick initialization in .

What you need to do is add click events on your button. To do that you'll need addEventListener and attachEvent (ie) methods.

<!DOCTYPE html>
<html>
<head>
    <script>
        function addEvent(obj, event, func) {
            if (obj.addEventListener) {
                obj.addEventListener(event, func, false);
                return true;
            } else if (obj.attachEvent) {
                obj.attachEvent('on' + event, func);
            } else {
                var f = obj['on' + event];
                obj['on' + event] = typeof f === 'function' ? function() {
                    f();
                    func();
                } : func
            }
        }

        function f1()
        {
            alert("f1 called");
            //form validation that recalls the page showing with supplied inputs.    
        }
    </script>
</head>
<body>
    <form name="form1" id="form1" method="post">
        State: <select id="state ID">
        <option></option>
        <option value="ap">ap</option>
        <option value="bp">bp</option>
        </select>
    </form>

    <table><tr><td id="Save" onclick="f1()">click</td></tr></table>

    <script>
        addEvent(document.getElementById('Save'), 'click', function() {
            alert('hello');
        });
    </script>
</body>
</html>

回答6:

function validate() {

    if( document.myForm.phonenumber.value == "" ) {
        alert( "Please provide your phonenumber!" );
        phonenumber.focus;
        return false;
    }
    if (/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/.test(myForm.email.value))  {  
        return (true)  
    }  
    alert("You have entered an invalid email address!");
    return (false);
}

来源：https://stackoverflow.com/questions/21477717/how-to-call-a-js-function-using-onclick-event

标签

javascript

html

forms

validation

html-validation