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forbidden to set this for setTimeout #2511

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merged 2 commits into from Jun 13, 2019
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forbidden to set this for setTimeout #2511

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fcbe88f
forbidden to set `this` for setTimeout
justjavac Jun 13, 2019
ce71f9c
clean code
justjavac Jun 13, 2019
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11 changes: 11 additions & 0 deletions js/timers.ts
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Expand Up @@ -181,6 +181,13 @@ function fireTimers(): void {

export type Args = unknown[];

// @internal
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function checkThis<T>(thisArg: T): void {
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if (thisArg !== null && thisArg !== undefined && thisArg !== window) {
throw new TypeError("Illegal invocation");
}
}

function setTimer(
cb: (...args: Args) => void,
delay: number,
Expand Down Expand Up @@ -226,6 +233,8 @@ export function setTimeout(
delay: number,
...args: Args
): number {
// @ts-ignore
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What error are you ignoring and why?

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Because I used this in a function(not a class)

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Possibly a helpful tip: you can put the reasoning for a ts-ignore on the same line:

example:

// @ts-ignore : because I used this in a function (not a class)
checkThis(this);

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@kitsonk kitsonk Jun 13, 2019 •
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Defining this in the arguments would remove this error. Under strict mode, where this cannot be inferred, you have to be explicit. It isn't an error to ignore.

function setTimer(
	this: unknown,
    cb: (...args: Args) => void,
	delay: number,
	...args: unknown[]
): number {
	checkThis(this);
	// ...
}

checkThis(this);
return setTimer(cb, delay, args, false);
}

Expand All @@ -235,6 +244,8 @@ export function setInterval(
delay: number,
...args: Args
): number {
// @ts-ignore
checkThis(this);
return setTimer(cb, delay, args, true);
}

Expand Down
54 changes: 54 additions & 0 deletions js/timers_test.ts
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Expand Up @@ -177,3 +177,57 @@ test(async function timeoutCallbackThis(): Promise<void> {
setTimeout(obj.foo, 1);
await promise;
});

test(async function timeoutBindThis(): Promise<void> {
function noop(): void {}

const thisCheckPassed = [null, undefined, window, globalThis];

const thisCheckFailed = [
0,
"",
true,
false,
{},
[],
"foo",
(): void => {},
Object.prototype
];

thisCheckPassed.forEach(
// eslint-disable-next-line @typescript-eslint/no-explicit-any
(thisArg: any): void => {
let hasThrown = 0;
try {
setTimeout.call(thisArg, noop, 1);
hasThrown = 1;
} catch (err) {
if (err instanceof TypeError) {
hasThrown = 2;
} else {
hasThrown = 3;
}
}
assertEquals(hasThrown, 1);
}
);

thisCheckFailed.forEach(
// eslint-disable-next-line @typescript-eslint/no-explicit-any
(thisArg: any): void => {
let hasThrown = 0;
try {
setTimeout.call(thisArg, noop, 1);
hasThrown = 1;
} catch (err) {
if (err instanceof TypeError) {
hasThrown = 2;
} else {
hasThrown = 3;
}
}
assertEquals(hasThrown, 2);
}
);
});