javascript - 如何从捕获的异常循环中返回值？

Question

let traveler = [{
    timestamp: 'qualia',
    firstname: 'unborn',
    lastname: 'child',
    location: 'null'
    },
    {
    timestamp: 1000,
    firstname: 'Olivia',
    lastname: 'Kirshner',
    location: 'Titan'
    },
    {
    timestamp: 1001,
    firstname: 'James',
    lastname: 'Cole',
    location: 'Emerson Hotel'
}]

// function noerror(splinter = traveler[0]) {
//     return [{firstname, lastname}] = splinter
// }

function restructure(time) {
    // if no array is returned on the lookup, and the value flags as undefined in restructure()
    let missingLink = traveler[0]
    let tempArray = traveler
        .filter((item) => item.timestamp === time)
    try {
        if (tempArray.firstname !== 'undefined' || tempArray.firstname !== 'null') { // check does not work
            return [{ firstname, lastname }] = tempArray

        } 
        // else {
        //     return [{firstname, lastname}] = missingLink
        // }
    } catch (e) {
        // e instanceof TypeError // boolean error type check
        switch (e.name) {
            case 'TypeError':
                console.error(`Could not complete your request: ${e.message}`);
                // return [{firstname, lastname}] = missingLink
            default:
                break;
        }
    } 
}

restructure(1001)
console.log(`firstname: ${firstname}, lastname: ${lastname}`)

restructure(100)
console.log(`firstname: ${firstname}, lastname: ${lastname}`)

restructure(1000)
lastname = 'Redforester' // temporary assignment to the variable, by value, not to the Object
console.log(`firstname: ${firstname}, lastname: ${lastname}`)

restructure(1000)

第 42 行让我头疼。

当传递给过滤器的搜索键生成空白数组时，我试图从捕获的异常循环中返回默认值。

该错误由 console.error() 处理，因此运行代码会显示错误是什么。

您知道一种允许从捕获的异常循环返回默认值的方法吗？

此行已被注释掉，但尝试它会导致新错误:

 return [{firstname, lastname}] = missingLink

Answer 1

使用filter返回一个数组。因此，tempArray 作为一个数组，没有 firstname 和 lastname 属性。

为此，我建议您将 filter() 切换为 find() 并在解构中删除 []:

let traveler = [{
    timestamp: 'qualia',
    firstname: 'unborn',
    lastname: 'child',
    location: 'null'
    },
    {
    timestamp: 1000,
    firstname: 'Olivia',
    lastname: 'Kirshner',
    location: 'Titan'
    },
    {
    timestamp: 1001,
    firstname: 'James',
    lastname: 'Cole',
    location: 'Emerson Hotel'
}]

// function noerror(splinter = traveler[0]) {
//     return [{firstname, lastname}] = splinter
// }

function restructure(time) {
    // if no array is returned on the lookup, and the value flags as undefined in restructure()
    let missingLink = traveler[0]
    let tempArray = traveler
        .find((item) => item.timestamp === time)
    
    try {
        if (tempArray.firstname !== 'undefined' || tempArray.firstname !== 'null') { // check does not work
          return { firstname, lastname } = tempArray

        } 
        // else {
        //     return [{firstname, lastname}] = missingLink
        // }
    } catch (e) {
        // e instanceof TypeError // boolean error type check
        switch (e.name) {
            case 'TypeError':
                console.error(`Could not complete your request: ${e.message}`);
                return {firstname, lastname} = missingLink
            default:
                break;
        }
    } 
}

restructure(1001)
console.log(`firstname: ${firstname}, lastname: ${lastname}`)

restructure(100)
console.log(`firstname: ${firstname}, lastname: ${lastname}`)

restructure(1000)
lastname = 'Redforester' // temporary assignment to the variable, by value, not to the Object
console.log(`firstname: ${firstname}, lastname: ${lastname}`)

restructure(1000)