chapter15中使用generator来实现异步化操作的同步化表达的例子

function* loadUI(){
    showLoadingScreen();
    yield loadUIDataAnsynchronously();
    hideLoadingScreen();
}

function showLoadingScreen(){
    console.log(‘show‘);
}

function hideLoadingScreen(){
    console.log(‘hide‘);
}

function loadUIDataAnsynchronously(){
    console.log(‘loading‘);
    process.nextTick(function(){
        console.log(‘loaded‘);
        it.next();
    });
}

var it = loadUI();
it.next();