util.promisify(original)

• original <Function>

• 返回:<Function>

  \Returns: <Function>

采用遵循常见的错误优先的回调风格的函数(也就是将 (err, value) => ... 回调作为最后一个参数),并返回一个返回 promise 的版本。

\Takes a function following the common error-first callback style, i.e. taking an (err, value) => ... callback as the last argument, and returns a version that returns promises.

import { promisify } from 'node:util';
import { stat } from 'node:fs';
const promisifiedStat = promisify(stat);
promisifiedStat('.').then((stats) => {
 // Do something with `stats`
}).catch((error) => {
 // Handle the error.
});const { promisify } = require('node:util');
const { stat } = require('node:fs');
const promisifiedStat = promisify(stat);
promisifiedStat('.').then((stats) => {
 // Do something with `stats`
}).catch((error) => {
 // Handle the error.
});拷贝

或者,等效地使用 async function:

\Or, equivalently using async functions:

import { promisify } from 'node:util';
import { stat } from 'node:fs';
const promisifiedStat = promisify(stat);
async function callStat() {
 const stats = await promisifiedStat('.');
 console.log(`This directory is owned by ${stats.uid}`);
}
callStat();const { promisify } = require('node:util');
const { stat } = require('node:fs');
const promisifiedStat = promisify(stat);
async function callStat() {
 const stats = await promisifiedStat('.');
 console.log(`This directory is owned by ${stats.uid}`);
}
callStat();拷贝

如果存在 original[util.promisify.custom] 属性,promisify 将返回其值,请参阅 自定义 promise 化函数。

\If there is an original[util.promisify.custom] property present, promisify will return its value, see Custom promisified functions.

promisify() 假设 original 是在所有情况下都将回调作为其最后一个参数的函数。如果 original 不是函数,则 promisify() 将抛出错误。如果 original 是函数,但其最后一个参数不是错误优先的回调,则它仍然会被传入错误优先的回调作为其最后一个参数。

\promisify() assumes that original is a function taking a callback as its final argument in all cases. If original is not a function, promisify() will throw an error. If original is a function but its last argument is not an error-first callback, it will still be passed an error-first callback as its last argument.

除非经过特殊处理,否则在类方法或其他使用 this 的方法上使用 promisify() 可能无法按预期工作:

\Using promisify() on class methods or other methods that use this may not work as expected unless handled specially:

import { promisify } from 'node:util';
class Foo {
 constructor() {
 this.a = 42;
 }
 bar(callback) {
 callback(null, this.a);
 }
}
const foo = new Foo();
const naiveBar = promisify(foo.bar);
// TypeError: Cannot read properties of undefined (reading 'a')
// naiveBar().then(a => console.log(a));
naiveBar.call(foo).then((a) => console.log(a)); // '42'
const bindBar = naiveBar.bind(foo);
bindBar().then((a) => console.log(a)); // '42'const { promisify } = require('node:util');
class Foo {
 constructor() {
 this.a = 42;
 }
 bar(callback) {
 callback(null, this.a);
 }
}
const foo = new Foo();
const naiveBar = promisify(foo.bar);
// TypeError: Cannot read properties of undefined (reading 'a')
// naiveBar().then(a => console.log(a));
naiveBar.call(foo).then((a) => console.log(a)); // '42'
const bindBar = naiveBar.bind(foo);
bindBar().then((a) => console.log(a)); // '42'拷贝