Onclick not working for javascript function which takes function as argument?

Question

Code

html

<button onclick="getUserIP(function(ip))">Click me</button>

<p id="demo"></p>

script

/**
 * Get the user IP throught the webkitRTCPeerConnection
 * @param onNewIP {Function} listener function to expose the IP locally
 * @return undefined
 */
function getUserIP(onNewIP) { //  onNewIp - your listener function for new IPs
    //compatibility for firefox and chrome
    var myPeerConnection = window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection;
    var pc = new myPeerConnection({
        iceServers: []
    }),
    noop = function() {},
    localIPs = {},
    ipRegex = /([0-9]{1,3}(\.[0-9]{1,3}){3}|[a-f0-9]{1,4}(:[a-f0-9]{1,4}){7})/g,
    key;

    function iterateIP(ip) {
        if (!localIPs[ip]) onNewIP(ip);
        localIPs[ip] = true;
    }

     //create a bogus data channel
    pc.createDataChannel("");

    // create offer and set local description
    pc.createOffer(function(sdp) {
        sdp.sdp.split('\n').forEach(function(line) {
            if (line.indexOf('candidate') < 0) return;
            line.match(ipRegex).forEach(iterateIP);
        });
        
        pc.setLocalDescription(sdp, noop, noop);
    }, noop); 

    //listen for candidate events
    pc.onicecandidate = function(ice) {
        if (!ice || !ice.candidate || !ice.candidate.candidate || !ice.candidate.candidate.match(ipRegex)) return;
        ice.candidate.candidate.match(ipRegex).forEach(iterateIP);
    };
}

// Usage

getUserIP(function(ip){
        document.getElementById("demo").innerHTML = 'Got your IP ! : '  + ip + " | verify in http://www.whatismypublicip.com/";
});

and Demo jsfidle

I'm trying to get private ip of end-user who clicks on this button.

As I run the code, it gives me no output. Basically I don't know the syntax to call a js function which takes function as an argument. Thanks.

update

<button id="a" onclick=(function(ip)
{
document.getElementById("demo").innerHTML = + ip;
})();> Clickme </button>
<p id="demo"></p>

error

"<a class='gotoLine' href='#41:20'>41:20</a> Uncaught SyntaxError: Unexpected end of input"

function(ip) is not a valid function definition and will throw a SyntaxError. If you really want to define the callback within the onclick attribute try this: function(ip) { /* your code */ } — Đinh Carabus
– Đinh Carabus, Commented Nov 24, 2020 at 19:38
@subarachnid is right, onclick="getUserIP(function(ip)) makes no sense, as getUserIP's parameter needs to be an actual function. — Δ O
– Δ O, Commented Nov 24, 2020 at 19:44
@subarachnid i tried but it gives me error pls see code above — user316389
– user316389, Commented Nov 24, 2020 at 20:20

Đinh Carabus · Accepted Answer · 2020-11-28 00:32:05Z

1

You forgot to call the getUserIP function and you'll also have to put the attribute value in quotes ("..."). For the ('demo') part you then have to use single quotes. Try this:

// just a demo function (you can ignore this)
const getUserIP = f => f("it works!")

<button id="a" onclick="getUserIP(function(ip) {
   document.getElementById('demo').innerHTML = ip;
});"> Clickme </button>

<p id="demo"></p>

edited Nov 28, 2020 at 0:32

answered Nov 24, 2020 at 20:42

Đinh Carabus

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