Working with Typescript: creating closures within a loop

Question

Working with Typescript: creating closures within a loop

I've encountered a challenge while attempting to incorporate closures in Typescript within a loop. The issue I'm facing is quite significant.

for(let car of vehicles) {
    update(location => 
        {
            car.location = location;
        }
    );
}

When compiling using Typescript 1.8.1 and targeting ES5, the following error emerges:

Loop contains block-scoped variable 'car' referenced by a function in the loop. This is only supported in ECMAScript 6 or higher.

Using var instead of let in the loop results in all closures utilizing the last value of car. Are there any effective workarounds for this issue when targeting ES5?

typescript

Answer 1

Answer №1

Is there a viable solution for this issue when targeting ES5?

We recommend upgrading to TypeScript nightly. This functionality is currently available in that version and will be included in future releases.

Learn More

For additional information, visit: https://basarat.gitbooks.io/typescript/content/docs/getting-started.html#nightly-typescript

Answer 2

Is there a viable solution for this issue when targeting ES5?

We recommend upgrading to TypeScript nightly. This functionality is currently available in that version and will be included in future releases.

Learn More

For additional information, visit: https://basarat.gitbooks.io/typescript/content/docs/getting-started.html#nightly-typescript

Answer 3

Answer №2

The issue arises from the fact that the function being called in the update is linked to the variable 'vehicle', rather than the specific vehicle being iterated over in the loop. To address this, you could try something along these lines:

for(let car of cars) {
    (carClosure => {
        update(position => carClosure.position = position)
    })(car)
}

Alternatively, you could utilize a JavaScript runtime that supports scoping with let, which would likely yield the desired outcome.

Answer 4

The issue arises from the fact that the function being called in the update is linked to the variable 'vehicle', rather than the specific vehicle being iterated over in the loop. To address this, you could try something along these lines:

for(let car of cars) {
    (carClosure => {
        update(position => carClosure.position = position)
    })(car)
}

Alternatively, you could utilize a JavaScript runtime that supports scoping with let, which would likely yield the desired outcome.

Answer 5

Answer №3

Indeed, by binding the function utilizing the closure variable, a distinct vehicle reference will be generated for each of the internal functions within the loop

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind

for(let car of vehicles) {
    update(function(vehicle, location)  {
        vehicle.location = location;
    }.bind(null, car));
}

Answer 6

Indeed, by binding the function utilizing the closure variable, a distinct vehicle reference will be generated for each of the internal functions within the loop

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind

for(let car of vehicles) {
    update(function(vehicle, location)  {
        vehicle.location = location;
    }.bind(null, car));
}

Working with Typescript: creating closures within a loop

Answer №1

Learn More

Answer №2

Answer №3

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