JS模擬實現枚舉

前言

在當前的JavaScript中，並沒有枚舉這個概念，在某些場景中使用枚舉更能保證數據的正確性，減少數據校驗過程，下面就介紹一下JavaScript如何模擬實現枚舉效果。

 

枚舉主要特點

1. 枚舉值不能重復
2. 不能被修改

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實現

let days; (function (days) { days[days["Sunday"] = 0] = "Sunday"; days[days["Monday"] = 1] = "Monday"; days[days["Tuesday"] = 2] = "Tuesday"; days[days["Wednesday"] = 3] = "Wednesday"; days[days["Thursday"] = 4] = "Thursday"; days[days["Friday"] = 5] = "Friday"; days[days["Saturday"] = 6] = "Saturday"; })(days || (days = {})); 

這個時候days對象基本實現了枚舉效果，可以通過枚舉值或索引去訪問days對象，但枚舉有個重要特別是不能被修改，這個時候days是可以隨意修改的；可以通過Object.freeze函數讓對象不改修改，重新導出一個不可以修改的對象，完整代碼如下：

let days; (function (days) { days[days["Monday"] = 1] = "Monday"; days[days["Tuesday"] = 2] = "Tuesday"; days[days["Wednesday"] = 3] = "Wednesday"; days[days["Thursday"] = 4] = "Thursday"; days[days["Friday"] = 5] = "Friday"; days[days["Saturday"] = 6] = "Saturday"; days[days["Sunday"] = 0] = "Sunday"; })(days || (days = {})); //導出可枚舉對象 export EnumWeek = Object.freeze(days)