javascript - 将参数绑定(bind)到函数javascript

Question

当第一个查询像这样解决时，我正在尝试运行第二个查询:

const fn1 = secondQuery => $.get('1.json', data => secondQuery());
const fn2 = secondQuery => $.get('2.json', data => secondQuery());
const fn3 = secondQuery => $.get('3.json', data => secondQuery());
const fn4 = secondQuery => $.get('4.json', data => secondQuery());

const queries = [fn1, fn2, fn3, fn4];

const queriesWithArgs = queries.map((queryFn, index, arr) => {
    const nextQuery = arr[index + 1];

    if (!nextQuery) {
        return
    }

    return queryFn.bind(queryFn, nextQuery);
});

queriesWithArgs[0]();

但仍然收到错误 TypeError: secondQuery is not a function, while requests to 1.json and 2.json works fine fn2 seems to not receive fn3 as argument.你能解释一下它是如何工作的吗？

Answer 1

您似乎认为 arr 参数指的是 queriesWithArgs 数组，因此您可以从那里获取 nextQuery。它不是，它指的是原始 queries 数组，您正在调用那些 nextQuery 函数而无需进一步的参数。

相反，此处使用的正确工具是 reduceRight ，而不是 map，其中 nextQuery 累加器确实会引用之前的结果(或初始值，这里是 last 回调):

const queries = [fn1, fn2, fn3, fn4];

const run = queries.reduceRight((nextQuery, queryFn) => {
    return queryFn.bind(null, nextQuery);
}, function last() {
    console.log("done");
});

run();