How can I write a generator in a JavaScript class?
Edit: Add more examples.
Your class definition is (almost) correct.The error was in instantiation var Reply = new Reply();. This tries to redefine variable assigned to class name. Also generator function is expected to yield something. I elaborated a little OP code to show working example.
class Reply {
//added for test purpose
constructor(...args) {
this.args = args;
}
* getReply(msg) {
for (let arg in this.args) {
let reply = msg + this.args[arg];
//generator should yield something
yield reply;
}
//next call returns (yields) {done:true,value:undefined}
}
* otherFun() {
yield this.getReply('Nice to meet you '); //yields Generator object
yield this.getReply('See you '); //Yes, this can access
//next call yields {done:true, value:undefined}
}
* evenMore() {
yield* this.getReply('I miss you '); //yields generator result(s)
yield* this.getReply('I miss you even more ');
}
}
//now test what we have
const reply = new Reply('Peter', 'James', 'John');
//let and var here are interchangeable because of Global scope
var r = reply.getReply('Hello ');
var msg = r.next(); //{done:false,value:"..."}
while (!msg.done) {
console.log(msg.value);
msg = r.next();
}
var other = reply.otherFun();
var o = other.next(); //{done:false,value:Generator}
while (!o.done) {
let gen = o.value;
msg = gen.next();
while (!msg.done) {
console.log(msg.value);
msg = gen.next();
}
o = other.next();
}
var more = reply.evenMore();
msg = more.next();
while (!msg.done) {
console.log(msg.value);
msg = more.next();
}
//update of 1/12/2019
//more examples
for (let r of reply.getReply('for ')) {
console.log(r);
}
for (let r of reply.evenMore()) {
console.log(r);
}
//note that the following doesn't work because of lack of star (*) inside the generator function
for (let r of reply.otherFun()) {
console.log(r);
}UPDATE 1/12/2019
As suggested by @BugBuddy for..of loop looks even nicer (But doesn't work in all cases). See updated lines in the snippet.
TL; DR for confused visitors from Google:
In Javascript, how do I write a generator function in a class?
class A {
* values() {
yield "a value";
yield* [1, 2, 3, 4, 5];
}
}
is syntactically correct. It works. You’re welcome and now dismissed.