no-promise-executor-return
Disallow returning values from Promise executor functions
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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:
Open in Playground
/*eslint no-promise-executor-return: "error"*/
/*eslint-env es6*/
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:
Open in Playground
/*eslint no-promise-executor-return: "error"*/
/*eslint-env es6*/
// 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 totrue(falseby default), this rule will allow returning void values.
allowVoid
Examples of correct code for this rule with the { "allowVoid": true } option:
Open in Playground
/*eslint no-promise-executor-return: ["error", { allowVoid: true }]*/
/*eslint-env es6*/
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));
Related Rules
Version
This rule was introduced in ESLint v7.3.0.
Further Reading