ES6 Generator data types in JavaScript _javascript tips

1. Generator Introduction

Generator is a new data type introduced by ES6 that looks like a function that yield can be returned multiple times except by returning with return.

Generator is defined by the function*, (note the * number),

2. Example

function cannot save state, sometimes need global variable to save number;

2.1

' Use strict ';
function next_id () {
var id = 1;
while (id<100) {
yield id;
id++;
}
return ID;
}
Test:
var
x, pass
= True,
g = next_id ();
for (x = 1; x < x + +) {
if (G.next (). Value!== x) {Pass
= false;
Alert (' Test failed! ');
break;
}
}
if (pass) {
alert (' Test passed! ');

2.2 An infinite loop of iterators

function* Idmaker () {
var index = 0;
while (true)
yield index++;
var Gen = Idmaker (); "Generator {}"
Console.log (Gen.next (). value);//0
Console.log (gen.next (). value);//1

2.3generator.prototype.next ()

When the iteration ends, Generator.next (). Done ===true, before the end ===false

Function* Gen () { 
yield 1;
Yield 2;
Yield 3;
}
var g = gen (); "Generator {}"
g.next ();//"Object {value:1, done:false}"
G.next ();//"Object {value:2, Done:false } "
G.next ();//" Object {value:3, done:false} "

2.4 Generator.prototype.return ();

The return method returns the given parameter value and ends the iterator

Example

Function* Gen () { 
yield 1;
Yield 2;
Yield 3;
}
var g = gen ();
G.next (); {value:1, done:false}
g.return ("foo");//{value: "foo", Done:true}

Note If the done value is true and then call return, the value returned is also undefined

Function* Gen () {yield 1;}
var g = gen ();
Console.log (G.next ());//{value:1, Done:false}
Console.log (G.next ());//{value:undefined, Done:true}

2.5 Generator.prototype.throw ()

Thorw () method, by throwing an exception into the iterator, to regain the execution of the iterator;

Returns an object with value and two properties

Function* Gen () {while
(true) {
try {
yield;
} catch (e) {
console.log ("Error caught!");
}
}
var g = gen ();
var a = G.next ();
{value:42, done:false}
var b = g.throw (new Error ("Something Went Wrong"));
"Error caught!"
{value:42, done:false}
Console.log (a);
Console.log (b.value+ "::" +b.done);

The above is a small set to introduce the JavaScript ES6 generator data types, I hope to help you, if you have any questions please give me a message, small series will promptly reply to everyone. Here also thank you very much for the cloud Habitat Community website support!