💾arr.containsSubarray()

💾 程式

💡 祕技：下面的 valueIsInArraySequentially 用了一個內含參數 i 的 closure，讓每次測試「一個值是否在陣列中」，都從新的位置開始搜尋：

// ⭐️ 注意：函數的參數都是變數(var)
// intial value of `i` = 0  ￣￣￣￣￣￣⤵︎
(i => v => i = this.indexOf(v, i) + 1)(0)

簡直是太聰明了👍

when calling array.containsSubarray(), this === array

• replit

// 🔸 arr.containsSubarray()
Array.prototype.containsSubarray = function(subarray, orderIsRelevant=false) {
    
    // ⭐ closure with internal parameter `i`
    const valueIsInArraySequentially = (i => v => i = this.indexOf(v, i) + 1)(0);
    
    const valueIsInArray = (v => this.includes(v));
    const valuePassedTest = orderIsRelevant ? valueIsInArraySequentially : valueIsInArray;
    return subarray.every(valuePassedTest);
};

• valueIsInArraySequentially is equivalent to:

// closure (with internal variable `startFromIndex`)
const valueInArraySequentially = (()=>{
    // internal variable in clusure
    let startFromIndex = 0;
    // when calling `array.containsSubarray()`, `this === array`
    return (value) => startFromIndex = this.indexOf(value, startFromIndex) + 1;
})();

💈範例

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