CODEWITHSUNDEEP
javascriptjqueryevent-listener
HenrijsS
HenrijsS

Reputation: 674

Javascript on function call

My client's webshop has a custom product configurator which has a window.build_preview function.

This method can be called whenever, but I want to check when it's called. jQuery has an .on method, but it only applies to DOM eventlisteners.

Is it possible to listen for function calls in JS? For example:

$(window).on(build_preview(), function() {
   alert('Function has been called somewhere else!');
})

Upvotes: 0

Views: 233

Answers (2)

charlietfl
charlietfl

Reputation: 171679

You can overload the original function and trigger a custom event in the new version and add an event listener for the custom event.

Just make sure that the original is already declared prior to your overload code

// original function declaration
window.build_preview = function(){
   console.log('.build_preview() called')
}

// store reference to original function
const origFn = window.build_preview

// overload the function
window.build_preview = function(){
   // call original
   origFn();
   // trigger custom event
   $(window).trigger('build_preview')
}
// custom event listener
$(window).on('build_preview', function(){
    console.log('event triggered from build_preview() call');
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<button onclick="build_preview()">Click me</button>

Upvotes: 1

Shreyash bhatt
Shreyash bhatt

Reputation: 156

You can create and dispatch a custom event

const event = new Event('build_preview');

// Listen for the event.
window.addEventListener('build_preview', 
    function (e) { 
        alert("function has been called somewhere else") 
    },
    false);

// Dispatch the event inside your function build_preview so that whenever it 
// is called this event is emitted.
window.dispatchEvent(event);

for more info check this

Upvotes: 1

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