generator 可以返回多次的函數(shù)
function* foo(x) {
yield x + 1;
yield x + 2;
return x + 3;
}
舉列 斐波那契數(shù)列
function fib(max) {
var
t,
a = 0,
b = 1,
arr = [0, 1];
while (arr.length < max) {
t = a + b;
a = b;
b = t;
arr.push(t);
}
return arr;
}
// 測(cè)試:
fib(5); // [0, 1, 1, 2, 3]
fib(10); // [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
function* fib(max) {
var
t,
a = 0,
b = 1,
n = 1;
while (n < max) {
yield a;
t = a + b;
a = b;
b = t;
n ++;
}
return a;
}
調(diào)用generator對(duì)象
第一種
var f = fib(5);
f.next(); // {value: 0, done: false}
f.next(); // {value: 1, done: false}
f.next(); // {value: 1, done: false}
f.next(); // {value: 2, done: false}
f.next(); // {value: 3, done: true}
f.next().value
done表示這個(gè)generator是否已經(jīng)執(zhí)行結(jié)束
如果done為true，則value就是return的返回值
第二種
for (var x of fib(5)) {
console.log(x); // 依次輸出0, 1, 1, 2, 3
}
generator可以實(shí)現(xiàn)面向?qū)ο蟛拍軐?shí)現(xiàn)的功能
練習(xí)：自增ID
var current_id = 0;
function next_id() {
current_id ++;
return current_id;
}
'use strict';
function* next_id() {
var id = 1;
while (true) {
yield id++;
}
return true;
}
var g=next_id();
for(var x=1;x<10;x++){
alert(g.next().value);
}//1 2 3 4 5 6 7 8 9
// 測(cè)試:
var
x,
pass = true,
g = next_id();
for (x = 1; x < 100; x ++) {
if (g.next().value !== x) {
pass = false;
alert('測(cè)試失敗!');
break;
}
}
if (pass) {
alert('測(cè)試通過(guò)!');
}
