no-promise-executor-return.md

title	rule_type	related_rules	further_reading
no-promise-executor-return	problem	no-async-promise-executor	https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise

The new Promise constructor accepts a single argument, called an executor.

const myPromise = new Promise(function executor(resolve, reject) {
    readFile('foo.txt', function(err, result) {
        if (err) {
            reject(err);
        } else {
            resolve(result);
        }
    });
});

The executor function usually initiates some asynchronous operation. Once it is finished, the executor should call resolve with the result, or reject if an error occurred.

The return value of the executor is ignored. Returning a value from an executor function is a possible error because the returned value cannot be used and it doesn't affect the promise in any way.

Rule Details

This rule disallows returning values from Promise executor functions.

Only return without a value is allowed, as it's a control flow statement.

Examples of incorrect code for this rule:

::: incorrect

/*eslint no-promise-executor-return: "error"*/

new Promise((resolve, reject) => {
    if (someCondition) {
        return defaultResult;
    }
    getSomething((err, result) => {
        if (err) {
            reject(err);
        } else {
            resolve(result);
        }
    });
});

new Promise((resolve, reject) => getSomething((err, data) => {
    if (err) {
        reject(err);
    } else {
        resolve(data);
    }
}));

new Promise(() => {
    return 1;
});

new Promise(r => r(1));

:::

Examples of correct code for this rule:

::: correct

/*eslint no-promise-executor-return: "error"*/

// Turn return inline into two lines
new Promise((resolve, reject) => {
    if (someCondition) {
        resolve(defaultResult);
        return;
    }
    getSomething((err, result) => {
        if (err) {
            reject(err);
        } else {
            resolve(result);
        }
    });
});

// Add curly braces
new Promise((resolve, reject) => {
    getSomething((err, data) => {
        if (err) {
            reject(err);
        } else {
            resolve(data);
        }
    });
});

new Promise(r => { r(1) });
// or just use Promise.resolve
Promise.resolve(1);

:::

Options

This rule takes one option, an object, with the following properties:

• allowVoid: If set to true (false by default), this rule will allow returning void values.

allowVoid

Examples of correct code for this rule with the { "allowVoid": true } option:

::: correct

/*eslint no-promise-executor-return: ["error", { allowVoid: true }]*/

new Promise((resolve, reject) => {
    if (someCondition) {
        return void resolve(defaultResult);
    }
    getSomething((err, result) => {
        if (err) {
            reject(err);
        } else {
            resolve(result);
        }
    });
});

new Promise((resolve, reject) => void getSomething((err, data) => {
    if (err) {
        reject(err);
    } else {
        resolve(data);
    }
}));

new Promise(r => void r(1));

:::