Day15 - 2725.Interval Cancellation 間隔取消 EASY

Description❓

Given a function fn, an array of arguments args, and an interval time t, return a cancel function cancelFn.

The function fn should be called with args immediately and then called again every t milliseconds until cancelFn is called at cancelT ms.

給定一個函數fn、一個參數陣列args和一個間隔時間t作為參數，並回傳一個取消函數cancelFn。
應立即使用args作為參數呼叫函數fn，然後間隔t 毫秒再次呼叫，直到在cancelT毫秒呼叫cancelFn。

Points

• 30Days of JS 工具書－setInterval(callback, delay, param…) 間隔時間內重複調用

Solution✍️

[ ▶️挑戰這一題 ][ 本日代碼 ]

let result=[];
var cancellable = function (fn, args, t) {
    let startTime = Date.now(); 

    //宣告`callFn`-被調用時會呼叫`fn(...args)`並打印紀錄    
    let callFn =(...args) => {
        let returnedVal = fn(...args);
        const currentTime = Date.now(); 
        const elapsedTime = currentTime - startTime;
        console.log(`times:${elapsedTime},returned:${returnedVal}`);
        result.push( {
            'time':elapsedTime,
            'returned':returnedVal,
        });
    }
    callFn(...args); //第一次調用函數`callFn`
    startTime = Date.now(); 

    // 設定間隔幾秒調用一次`callFn`
    let intervalID = setInterval(() => {
        callFn(...args);
    }, t);

    //宣告`cancelFn`-被調用時會啟動倒計時以`取消間隔調用`
    let cancelFn = () => {
        clearInterval(intervalID);
    };

    return cancelFn;
};

Testcase

let fn = (x) => x * 2;
let args = [4];
let t = 35; // t 单位是毫秒 0 35 70 105 140 175 
const cancel = cancellable(fn, args, t);

let cancelT = 190; // cancelT 单位是毫秒  
setTimeout(() => {
    cancel();
    console.log(result);
}, cancelT);

// output
// (6) [{…}, {…}, {…}, {…}, {…}, {…}]
// 0: {time: 0, returned: 8}
// 1: {time: 47, returned: 8}
// 2: {time: 78, returned: 8}
// 3: {time: 109, returned: 8}
// 4: {time: 156, returned: 8}
// 5: {time: 187, returned: 8}

let fn = (x1, x2) => (x1 * x2);
let args = [2, 5];
let t = 30; // t 单位是毫秒 0 35 60 90 120 150 
const cancel = cancellable(fn, args, t);

let cancelT = 165; // cancelT 单位是毫秒  
setTimeout(() => {
    cancel();
    console.log(result);
}, cancelT);

// output
// (6) [{…}, {…}, {…}, {…}, {…}, {…}]
// 0: {time: 0, returned: 10}
// 1: {time: 31, returned: 10}
// 2: {time: 61, returned: 10}
// 3: {time: 90, returned: 10}
// 4: {time: 120, returned: 10}
// 5: {time: 151, returned: 10}

let fn = (x1, x2, x3) => (x1 + x2 + x3);
let args = [5, 1, 3];
let t = 50; // t 单位是毫秒 0 50 100 150
const cancel = cancellable(fn, args, t);

let cancelT = 180; // cancelT 单位是毫秒  
setTimeout(() => {
    cancel();
    console.log(result);
}, cancelT);

//output
// (4) [{…}, {…}, {…}, {…}]
// 0: {time: 0, returned: 9}
// 1: {time: 64, returned: 9}
// 2: {time: 110, returned: 9}
// 3: {time: 156, returned: 9}