JavaScript設計模式 - Strategy

專職寫了幾個月，雖然開始有些凌亂，現在基本上也認同：JavaScript是一門優雅的語言。

從設計模式的角度，應該能更好地理解JavaScript的不同，改善既有代碼。

那就先從比較常用的Strategy模式開始。

Strategy Pattern

Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from the clients that use it.

(From https://sourcemaking.com/design_patterns/strategy)

JavaScript Example

• 定義一組Strategy, 確保可互相替換
• 通過替換Strategy改變程序的行爲

        const HelloWork = function (travelStrategy) {
            this.travelStrategy = travelStrategy;

            this.setTravelStrategy = function (travelStrategy) {
                this.travelStrategy = travelStrategy;
            };
            this.travel = function () {
                let strategy = this.travelStrategy();
                console.log(`${strategy}上班`);
            };
        };

        const walking = () => {
            return '我窮我走路';
        };
        const bike = () => {
            return '我環保我開新能源機動車（小電瓶）';
        };
        const subway = () => {
            return '我土豪我搭幾個億的地鐵';
        };

        const hw = new HelloWork(walking);
        hw.travel();

        hw.setTravelStrategy(bike);
        hw.travel();

        hw.setTravelStrategy(subway);
        hw.travel();

Output:

我窮我走路上班
我環保我開新能源機動車（小電瓶）上班
我土豪我搭幾個億的地鐵上班