Practice Event Emitter
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Event Emitter
Implement EventEmitter with subscribe(eventName, callback) and emit(eventName, args). Multiple distinct callbacks may subscribe to one event. subscribe returns an object whose unsubscribe() removes that callback and returns undefined. emit calls the event's current callbacks in subscription order with the optional args array spread as their arguments, and returns their results in the same order. Use an empty argument list when args is omitted. With no subscribers, return an empty array.
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Understanding the Event Emitter Problem
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Problem Statement
Implement EventEmitter with subscribe(eventName, callback) and emit(eventName, args). Multiple distinct callbacks may subscribe to one event. subscribe returns an object whose unsubscribe() removes that callback and returns undefined. emit calls the event's current callbacks in subscription order with the optional args array spread as their arguments, and returns their results in the same order. Use an empty argument list when args is omitted. With no subscribers, return an empty array.
Source: Event Emitter on LeetCode. Use the original task for its coding environment and submissions.
Event Emitter
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Examples
# Example 1
actions = ["EventEmitter", "emit", "subscribe", "subscribe", "emit"], values = [[], ["firstEvent"], ["firstEvent", "function cb1() { return 5; }"], ["firstEvent", "function cb1() { return 6; }"], ["firstEvent"]][[],["emitted",[]],["subscribed"],["subscribed"],["emitted",[5,6]]]
# Example 2
actions = ["EventEmitter", "subscribe", "emit", "emit"], values = [[], ["firstEvent", "function cb1(...args) { return args.join(','); }"], ["firstEvent", [1,2,3]], ["firstEvent", [3,4,6]]][[],["subscribed"],["emitted",["1,2,3"]],["emitted",["3,4,6"]]]
# Example 3
actions = ["EventEmitter", "subscribe", "emit", "unsubscribe", "emit"], values = [[], ["firstEvent", "(...args) => args.join(',')"], ["firstEvent", [1,2,3]], [0], ["firstEvent", [4,5,6]]][[],["subscribed"],["emitted",["1,2,3"]],["unsubscribed",0],["emitted",[]]]
# Example 4
actions = ["EventEmitter", "subscribe", "subscribe", "unsubscribe", "emit"], values = [[], ["firstEvent", "x => x + 1"], ["firstEvent", "x => x + 2"], [0], ["firstEvent", [5]]]
[[],["subscribed"],["subscribed"],["unsubscribed",0],["emitted",[7]]]
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