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

迭代构造器可以接受初值,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,

如果遇到 return 则迭代执行结束

迭代构造器继承自 Function , 因此 function 具备的用于修改执行体内的 this 指向 的 call、apply、bind 方法,迭代构造器也都具备,用法与 function 一样, 另外, 迭代构造器不允许访问 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:如果过yield* 后面的表达式是一个可迭代对象,则 yield*  操作会执行迭代操作而返回这个可迭代对象迭代完毕的结果。

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 }
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