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/**
* 申请缓存,并调用回调
*/
function cacheRequest(fn) {
let hasReq = 1; // 未申请 -1 申请中 -2 申请胜利 -3
let result = null;
const cals = [];
return function (...args) {const options = args[0];
const callback = args[1];
function myCallback(res) {
hasReq = 3;
result = res;
for (let i = 0; i < cals.length; i++) {cals[i](res);
}
}
console.log('hasReq', hasReq)
if (hasReq === 1) {
hasReq = 2
cals.push(callback);
fn(options, myCallback);
} else if (hasReq === 3) {callback(result);
} else {cals.push(callback);
}
}
}
// 应用 promise
function cacheRequest2(fn) {
let p = null;
return function (...args) {const [options, callback] = args;
if (!p) {p = new Promise((resolve) => {fn(options, (res) => {resolve(res);
})
})
}
p.then(callback);
}
}
// 应用示例
const fn = (options, callback) => {
// 发动申请等,而后调用 callback
setTimeout(() => {callback(1);
});
}
const cachedReq = cacheRequest2(fn)
cachedReq({}, (data) => {console.log('data', data);
})
cachedReq({}, (data) => {console.log('data', data);
})
setTimeout(() => {cachedReq({}, (data) => {console.log('data', data);
})
});
正文完
发表至: javascript
2021-06-18