wrap-by-promise

wrap-by-promise promisify function to receive callback.

It's works like util.promisify as default.

however, wrap-by-promise can promisify a function wich NOT apply to common error-first callback style!

Installation

npm i wrap-by-promise

Example

// test/test.js
// require wrap-by-promise
const wrap = require("../build/wrap-by-promise").wrapByPromise;
 
// fs.readFile : function to receive callback...
const { readFile } = require("fs");
readFile("./test/hello.txt", "utf-8", (err, data) => {
    if (err) throw err;
    console.log({ data });
});
 
// let's wrap above function!
// wrap-by-promise works like util.promisify as default.
const _readfile = wrap(readFile);
 
// and get promise!
_readfile("./test/hello.txt", "utf-8")
    .then(res => console.log({ res }))
    .catch(err => { throw err; });
 
// it's able to use in async function with await!
(async _ => {
    try {
        const data = await _readfile("./test/hello.txt", "utf-8");
        console.log({ data })
    } catch (e) {
        throw e;
    }
})();
 
// also, you can promisify a function which NOT apply to common error-first callback style!
const sleep = wrap(setTimeout, 0);
sleep(3000).then(_ => console.log("Hi!"));

API

wrapByPromise(func: Function, ?cbpos: number, ?errpos: number, ?names: Array<string>)

• func : Function to receive callback. If callback function got only one argument, Promise's resolve function get one value as argument. Otherwise, resolve function get an array as argument. If names argument was set, resolve function get object data.
• cbpos (optional) : The position of a callback on above function's arguments. The default value is func.length - 1.
• erropt (optional) : The position of error data on callback function's arguments. The default value is 0. If a callback function does not receive error data, you have to set this value to -1.
• names (optional) : The list of names of arguments which give to the callback. The default value is undefined.