在我看来，MDN文档非常好。

The function containing the yield keyword is a generator. When you call it, its formal parameters are bound to actual arguments, but its body isn't actually evaluated. Instead, a generator-iterator is returned. Each call to the generator-iterator's next() method performs another pass through the iterative algorithm. Each step's value is the value specified by the yield keyword. Think of yield as the generator-iterator version of return, indicating the boundary between each iteration of the algorithm. Each time you call next(), the generator code resumes from the statement following the yield.

Yield还可以使用协程框架来消除回调地狱。

function start(routine, data) {
    result = routine.next(data);
    if(!result.done) {
        result.value(function(err, data) {
            if(err) routine.throw(err); // continue next iteration of routine with an exception
            else start(routine, data);  // continue next iteration of routine normally
        });
    }
}

// with nodejs as 'node --harmony'
fs = require('fs');
function read(path) {
    return function(callback) { fs.readFile(path, {encoding:'utf8'}, callback); };
}

function* routine() {
    text = yield read('/path/to/some/file.txt');
    console.log(text);
}

// with mdn javascript 1.7
http.get = function(url) {
    return function(callback) { 
        // make xhr request object, 
        // use callback(null, resonseText) on status 200,
        // or callback(responseText) on status 500
    };
};

function* routine() {
    text = yield http.get('/path/to/some/file.txt');
    console.log(text);
}

// invoked as.., on both mdn and nodejs

start(routine());

异步javascript调用之间的依赖关系。

另一个关于如何使用yield的好例子。

函数请求(url) { Axios.get (url).then((response) => { it.next(响应); }) ｝ 函数* main() { Const result1 = yield request('http://some.api.com'); Const result2 = yield request('http://some.otherapi?Id =' + result1。id); console.log('您的响应是:' + result2.value); ｝ Var it = main(); it.next ()

举个简单的例子:

const strArr = ["red", "green", "blue", "black"];

const strGen = function*() {
    for(let str of strArr) {
        yield str;
    }
};

let gen = strGen();

for (let i = 0; i < 5; i++) {
    console.log(gen.next())
}

//prints: {value: "red", done: false} -> 5 times with different colors, if you try it again as below:

console.log(gen.next());

//prints: {value: undefined, done: true}

它用于迭代器生成器。基本上，它允许您使用过程代码制作(可能是无限的)序列。请参阅Mozilla的文档。

在我看来，MDN文档非常好。

The function containing the yield keyword is a generator. When you call it, its formal parameters are bound to actual arguments, but its body isn't actually evaluated. Instead, a generator-iterator is returned. Each call to the generator-iterator's next() method performs another pass through the iterative algorithm. Each step's value is the value specified by the yield keyword. Think of yield as the generator-iterator version of return, indicating the boundary between each iteration of the algorithm. Each time you call next(), the generator code resumes from the statement following the yield.