一句話
promise有點像OC的success的block和failure的block，resolve對應success，reject對應failure
下面，舉個栗子：
static GET(url){
return new Promise((resolve, reject)=>{
fetch(url)
.then(response=>response.json())
.then(result=>{
resolve(result);
})
.catch(error=>{
reject(error);
})
})
}
是不是很像oc的block，??，比如用OC:
- (void)getUrl:(NSString *)url success:(void (^)(id))success failure:(void (^)(id))failure{
//獲取數據...
if (success) {
success(result);
}
if (failure) {
failure(error);
}
}
延伸下，fetch方法有點類似OC的Masonry，他們都屬于鏈式語法
[view1 mas_makeConstraints:^(MASConstraintMaker *make) {
make.left.equalTo(superview.mas_left).with.offset(padding.left);
}];
