生成器看起来像这样：

function test() {
    // first part of function
    yield;
    // second part of function
    yield;
}

var gen = test(); // creating a generator

gen.next(); // execute first part

button.onclick = function () {
    gen.next(); // execute second part on button click
};

现场演示： http://jsfiddle.net/MQ9PT/

然而，这并不适用于Firefox。它将成为下一版的ECMAScript标准的一部分。

This however doesn't work beyond Firefox. It will become part of the ECMAScript standard in the next edition...