包含javascript中的枚举等效项的列表理解

Question

请问这段python代码的javascript中的等价物是什么？

guessed_index = [
        i for i, letter in enumerate(self.chosen_word)
        if letter == self.guess
    ]

枚举和列表理解在ES6等效项中都不存在，如何将这两个概念合并为一个

Answer 1

专注于问题的可迭代/enumerate部分，而不是正在执行的特定任务:您可以使用generator function实现Python's enumerate的JavaScript模拟，并通过for-of (如果愿意，也可以手动)使用生成的生成器(这是可迭代的超集)：

​

function* enumerate(it, start = 0) {
    let index = start;
    for (const value of it) {
        yield [value, index++];
    }
}

const word = "hello";
const guess = "l";
const guessed_indexes = [];
for (const [value, index] of enumerate(word)) {
    if (value === guess) {
        guessed_indexes.push(index);
    }
}
console.log(`guessed_indexes for '${guess}' in '${word}':`, guessed_indexes);

​

或者，您可以编写一个特定的生成器函数来执行查找匹配的任务：

​

function* matchingIndexes(word, guess) {
    let index = 0;
    for (const letter of word) {
        if (letter === guess) {
            yield index;
        }
        ++index;
    }
}

const word = "hello";
const guess = "l";
const guessed_indexes = [...matchingIndexes(word, guess)];

console.log(`guessed_indexes for '${guess}' in '${word}':`, guessed_indexes);

​

Answer 2

也许findIndex是有用的？

​

const word = "Hello";
const guess = "o";
const guessed_index = [...word].findIndex(letter => letter === guess);
console.log(guessed_index)

​

Answer 3

对于不精通python的潜在读者来说，为了清楚起见，下面是与您的理解相当的python循环：

guessed_index = []
i = 0
for letter in self.chosen_word:
    if letter == self.guess:
        guessed_index.append(i)
    i += 1