How could something equivalent to lock
in C# be implemented in JavaScript?
So, to explain what I'm thinking a simple use case is:
User clicks button B
. B
raises an onclick event. If B
is in event-state
the event waits for B
to be in ready-state
before propagating. If B
is in ready-state
, B
is locked and is set to event-state
, then the event propagates. When the event's propagation is complete, B
is set to ready-state
.
I could see how something close to this could be done, simply by adding and removing the class ready-state
from the button. However, the problem is that a user can click a button twice in a row faster than the variable can be set, so this attempt at a lock will fail in some circumstances.
Does anyone know how to implement a lock that will not fail in JavaScript?
Lock is a questionable idea in JS which is intended to be threadless and not needing concurrency protection. You're looking to combine calls on deferred execution. The pattern I follow for this is the use of callbacks. Something like this:
var functionLock = false;
var functionCallbacks = [];
var lockingFunction = function (callback) {
if (functionLock) {
functionCallbacks.push(callback);
} else {
$.longRunning(function(response) {
while(functionCallbacks.length){
var thisCallback = functionCallbacks.pop();
thisCallback(response);
}
});
}
}
You can also implement this using DOM event listeners or a pubsub solution.