thunk函数实现generator函数的自动执行
const fs = require("fs");
const Thunk = function (fn) {
return function (...args) { //这是readFileThunk函数
return function (callback) {
return fn.call(this, ...args, callback); // fs.readFile(...args, callback)
};
};
};
const readFileThunk = Thunk(fs.readFile); // 返回里面函数
function run(fn) {
var gen = fn();
function next(err, data) {
/*
开始执行yeild表达式--->readFileThunk的执行--> 返回最里层callback入参的函数
result就是{value:function(callback){return fn.call(this, ...args, callback)},done:false}
*/
var result = gen.next(data);
if (result.done) return;
/*
next作为callback继续执行
*/
result.value(next);
}
next();
}
const g = function* () {
const s1 = yield readFileThunk("./files/1.json");
console.log(s1.toString());
const s2 = yield readFileThunk("./files/2.json");
console.log(s2.toString());
const s3 = yield readFileThunk("./files/3.json");
console.log(s3.toString());
};
run(g);
