在完成函数本身的所有操作之前，Node 是否可以从函数调用中返回一个值?

Is it possible that the function could return the stream before the Read a large file statement has finished processing (the large file has been fully read from the file system and the stream has been added), or is Node smart enough to complete all statements before returning?

function moveFiles(){

    var gulp = require('gulp'),
        stream = require('merge-stream')();

    // Read a large file
    stream.add(gulp.src('src/large-file.txt')
        .pipe(gulp.dest('dest/'))
    );

    // Read a small file
    stream.add(gulp.src('src/small-file.txt')
        .pipe(gulp.dest('dest/'))
    );

    return (stream.isEmpty() ? null : stream);

}

推荐答案

在完成函数本身的所有操作之前，Node 是否可以从函数调用中返回一个值?

function x() {
    setTimeout(function () {
        console.log('x1'));
    }, 2000);
    console.log('x2');
    return;
    console.log('x3');
}

function y() {
    console.log('y1');
    return new Promise(function (resolve, reject) {
        setTimeout(function () {
            resolve('message from y()');
        }, 2000);
    });
    console.log('y2');
}

var promise = y();

promise.then(function (value) {
    console.log(value);
});