我要评论//promise延时顺序执行
var waitone = new promise(function(resolve, reject) {
settimeout(function(){ resolve(1)}, 1000);
});
var waitsecond = new promise(function(resolve, reject) {
settimeout(function(){ resolve(1)}, 1000);
});
waitone.then(function() {
console.log("hello"); // 1秒后输出"hello"
return new promise(function(resolve, reject) {
settimeout(function(){ resolve(1)}, 1000);
});
}).then(function() {
console.log("hi"); // 2秒后输出"hi"
});
new promise(function(resolve , reject) {
resolve(1);
}).then(function(val) {
console.log(val);
return new promise(function(resolve , reject) {
resolve(2);
});
}).then(function(val) {
console.log(val);
return new promise(function(resolve , reject) {
resolve(3);
});
}).then(function(val) {
console.log(val);
return new promise(function(resolve , reject) {
resolve(4);
});
}).then(function(val) {
console.log(val);
});
//输出：
// 1
// 2
// 3
// 4
下面代码中，settimeout(fn, 0)在下一轮“事件循环”开始时执行，promise.resolve()在本轮“事件循环”结束时执行，console.log('one')则是立即执行，因此最先输出。
settimeout(function () {
console.log('three');
}, 0);
promise.resolve().then(function () {
console.log('two');
});
console.log('one');
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