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timers: enable timers to be used as primitives #19683

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6 changes: 6 additions & 0 deletions doc/api/timers.md
Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,12 @@ of the Node.js application.

Returns a reference to the `Timeout`.

### timeout[Symbol.toPrimitive]()

When coercing a `Timeout` to a primitive, a primitive will be generated that can be used with the appropriate function that can be used to clear the `Timeout`. This allows enhanced compatibility with browser `setTimeout`, and `setInterval` implementations.
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Nit: Please wrap at 80 characters :)

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fixed

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Wrap at 80 cols.

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fixed


Returns a `number`.
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Put

* Returns: {integer}

right below the heading.

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fixed


## Scheduling Timers

A timer in Node.js is an internal construct that calls a given function after
Expand Down
24 changes: 23 additions & 1 deletion lib/timers.js
Original file line number Diff line number Diff line change
Expand Up @@ -145,6 +145,8 @@ const kRefed = Symbol('refed');
const refedLists = Object.create(null);
const unrefedLists = Object.create(null);

const KNOWN_TIMERS = Object.create(null);

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Extraneous line.

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fixed


// Schedule or re-schedule a timer.
// The item must have been enroll()'d first.
Expand Down Expand Up @@ -453,6 +455,12 @@ function rearm(timer, start = TimerWrap.now()) {


const clearTimeout = exports.clearTimeout = function(timer) {
if (typeof timer === 'number' || typeof timer === 'string') {
if (timer in KNOWN_TIMERS) {
clearTimeout(KNOWN_TIMERS[timer]);
}
return;
}
if (timer && timer._onTimeout) {
timer._onTimeout = null;
if (timer instanceof Timeout) {
Expand Down Expand Up @@ -496,7 +504,13 @@ exports.setInterval = function(callback, repeat, arg1, arg2, arg3) {
return timeout;
};

exports.clearInterval = function(timer) {
const clearInterval = exports.clearInterval = function(timer) {
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Why the addition of clearInterval variable? Doesn't seem used anywhere.

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was added in e32b969 as a bug fix to previous iteration

if (typeof timer === 'number' || typeof timer === 'string') {
if (timer in KNOWN_TIMERS) {
clearInterval(KNOWN_TIMERS[timer]);
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I think we may want to avoid accessing global.clearInterval here … maybe doing something like we do for clearTimeout, i.e. const clearInterval = exports.clearInterval = … is a good idea here too?

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ah yes, that would be a bug if that happened. I'm not 100% sure on why these functions are not named looking at them...

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Would timer = KNOWN_TIMERS[timer] work? This would avoid a recursion.

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fixed

}
return;
}
if (timer && timer._repeat) {
timer._repeat = null;
clearTimeout(timer);
Expand All @@ -521,6 +535,11 @@ function unrefdHandle(timer, now) {
return true;
}

Timeout.prototype[Symbol.toPrimitive] = function() {
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Why @@toPrimitive rather than valueOf?

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see https://codepen.io/bradleymeck/pen/eMMpdR?editors=0012 , .valueOf is not safe for using as a key. toPrimitive handles both string and number coercion.

const id = this[async_id_symbol];
KNOWN_TIMERS[id] = this;
return id;
};

Timeout.prototype.unref = function() {
if (this._handle) {
Expand Down Expand Up @@ -558,6 +577,9 @@ Timeout.prototype.ref = function() {

Timeout.prototype.close = function() {
this._onTimeout = null;
if (typeof this[async_id_symbol] === 'number') {
delete KNOWN_TIMERS[this[async_id_symbol]];
}
if (this._handle) {
if (destroyHooksExist() &&
typeof this[async_id_symbol] === 'number' &&
Expand Down
23 changes: 23 additions & 0 deletions test/parallel/test-timers-toPrimitive.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
'use strict';
const common = require('../common');
const assert = require('assert');

const timeout1 = setTimeout(common.mustNotCall(), 0);
const timeout2 = setInterval(common.mustNotCall(), 0);

assert.strictEqual(Number.isNaN(+timeout1), false);
assert.strictEqual(Number.isNaN(+timeout2), false);

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Can you check that +timeout1 === timeout1[Symbol.toPrimitive]()?

assert.notStrictEqual(`${timeout1}`, Object.prototype.toString.call(timeout1));
assert.notStrictEqual(`${timeout2}`, Object.prototype.toString.call(timeout2));

assert.notStrictEqual(+timeout1, +timeout2);

const o = {};
o[timeout1] = timeout1;
o[timeout2] = timeout2;
const keys = Object.keys(o);
assert.deepStrictEqual(keys, [`${timeout1}`, `${timeout2}`]);

clearTimeout(keys[0]);
clearInterval(keys[1]);