之前見(jiàn)過(guò)的一道Promise面試題的答案
function red(){
console.log('red');
}
function green(){
console.log('green');
}
function yellow(){
console.log('yellow');
}
var tic = function(timmer, cb){
return new Promise(function(resolve, reject) {
setTimeout(function() {
cb();
resolve();
}, timmer);
});
};
var d = new Promise(function(resolve, reject){resolve();});
var step = function(def) {
def.then(function(){
return tic(3000, red);
}).then(function(){
return tic(2000, green);
}).then(function(){
return tic(1000, yellow);
}).then(function(){
step(def);
});
}
step(d);
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