jQuery callbacks.has() Method
Last Updated :
10 Jul, 2020
The callbacks.has() method in jQuery is used to answer whether the list has any callbacks attached. If a callback is passed as an argument, then it answers whether it is on the list or not.
Syntax:
callbacks.has([callback])
Parameters:
- callback: The parameter defines the callback to search for, in the list.
Return Value: This method either returns true or false.
Example 1: This example returns “true” because ‘func’ is in the list.
<!DOCTYPE HTML>
<html>
<head>
<script src=
</script>
</head>
<body style="text-align:center;">
<h1 style="color:green;">
GeeksForGeeks
</h1>
<p>
JQuery | callbacks.has() method
</p>
<button onclick="Geeks();">
click here
</button>
<p id="GFG"></p>
<script>
var el_down = document.getElementById("GFG");
var res = "";
var callbacks = jQuery.Callbacks();
function Geeks() {
var func = function (val) {
res = res + "value passed is - " + val;
};
callbacks.add(func); // function added to list
callbacks.fire("gfg_1");
el_down.innerHTML = callbacks.has();
}
</script>
</body>
</html>
|
Output:
Example 2: This example returns “false” because ‘func2’ is not in the list.
<!DOCTYPE HTML>
<html>
<head>
<script src=
</script>
</head>
<body style="text-align:center;">
<h1 style="color:green;">
GeeksForGeeks
</h1>
<p>
JQuery | callbacks.has() method
</p>
<button onclick="Geeks();">
click here
</button>
<p id="GFG_DOWN"></p>
<script>
var el_down = document.getElementById("GFG_DOWN");
var res = "";
var callbacks = jQuery.Callbacks();
function Geeks() {
var func1 = function (val) {
res = res + "value passed is - " + val;
};
var func2 = function (val) {
res = res + "value passed is - " + val;
};
// Function added to list
callbacks.add(func1);
callbacks.fire("gfg_1");
el_down.innerHTML = callbacks.has(func2);
}
</script>
</body>
</html>
|
Output:
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