ecma6 yield

function * generator(k){
   console.log('begin');
   var x = yield k;
   console.log('x:',x);
   var y = yield x+k;
   console.log('y:',y);
   return x+y+k;
}


var o = generator(1);
var r = o.next();
console.log('1:'+r.value, 'done:'+r.done);
r = o.next(3);
console.log('2:'+r.value,'done:'+r.done);
r = o.next(5);
console.log('3:'+r.value,'done:'+r.done);

//log
begin
1:1 done:false
x: 3
2:4 done:false
y: 5
3:9 done:true

===========================================================================
function * generator(k){
   console.log('begin');
   var x = yield k;
   console.log('x:',x);
   return 'end';
   var y = yield x+k;
   console.log('y:',y);
   return x+y+k;
}

var o = generator(1);
var r = o.next();
console.log('1:'+r.value,'done:'+r.done);
r = o.next(3);
console.log('2:'+r.value,'done:'+r.done);
r = o.next(5);
console.log('3:'+r.value,'done:'+r.done);

//log
begin
1:1 done:false
x: 3
2:end done:true
3:undefined done:true

 

迭代构造器能够接受初值，在构造时传入而非首次调用 next 时，
yield 后面的值被返回，后继代码暂时中断，直到调用 next 方法，

yield 赋值表达式：在下一次调用 next 时将传入的值赋給变量，

若是遇到 return 则迭代执行结束

 

迭代构造器继承自 Function ， 所以 function 具有的用于修改执行体内的 this 指向 的 call、apply、bind 方法，迭代构造器也都具有，用法与 function 同样， 另外， 迭代构造器不容许访问 caller 属性

function fun(){
var g = function *(k){
console.log(arguments[0],arguments.length,arguments.callee)
   console.log(this);
   var x = yield 123;
   return x;
}

var o = g.call(({a:123,b:456}),888)
o.next()
o.next(999)
}

fun()

//log
888 1 function g(k)
Object {a: 123, b: 456}

　　

使用 yield* 表达式  执行可迭代对象：若是过yield* 后面的表达式是一个可迭代对象，则 yield*  操做会执行迭代操做二凡返回这个对象

function* g1() {
  yield 2;
  yield 3;
  yield 4;
}

function* g2() {
  yield 1;
  yield* g1();
  yield 5;
}

var iterator = g2();

console.log(iterator.next()); // { value: 1, done: false }
console.log(iterator.next()); // { value: 2, done: false }
console.log(iterator.next()); // { value: 3, done: false }
console.log(iterator.next()); // { value: 4, done: false }
console.log(iterator.next()); // { value: 5, done: false }
console.log(iterator.next()); // { value: undefined, done: true }