Javascript 如何在fetch-then/response函数中访问请求对象

我有一个JavaScript循环在数组上迭代。对于每个项目，我都执行一个提取请求来插入对象。如果服务器响应表明它是一个已插入的对象，我将尝试使用另一个获取调用执行更新操作

由于请求是异步的，在我尝试更新操作之前，循环会将请求对象设置为下一个插入项，因此我最终会请求对尚未插入的对象进行更新

是否有任何方法可以访问用于此获取操作的请求对象，以便使用该对象而不是循环变量

我在promise方法中尝试了

this

，但它返回了对window对象的引用：

console.log（this）=>>windowhttp://localhost

我的代码：

for (var i = 0; i < expectedRows; i++) {
    var row = myArray[i];
    customerCode = row['customer_code'];
    customerName = row['customer_name'];
    customerBalance = row['customer_balance'];
    // Build body call
    var callBody = {
        user: 'USER',
        code: customerCode,
        name: customerName,
        balance: customerBalance
    };
    var fetchOptions = {
        method: "POST",
        cache: "no-cache",
        headers: {
            "Content-Type": "application/x-www-form-urlencoded",
        },
        redirect: "error",
        referrer: "ux-import", 
        body: JSON.stringify(callBody),
    };
    // Call
    var epurl = baseEP + '/customer/create';
    fetch(epurl, fetchOptions)
    .then(response => response.json())
    .then(response => {
        console.log(this) // <== Window object reference
        if (response.error === 0) {
            console.log('insert ok');
            insertRows++;
        } else {
            if (response.error == 2) {
                console.log('insert error => update');
                var updateEP = baseEP + '/customer/update';
                fetch(updateEP, fetchOptions) // <== Not what you expect 
                .then(updResponse => updResponse.json())
                .then(updResponse => {
                    if (updResponse.error === 0) {
                        console.log('update ok.')
                        updateRows++;
                    } else {
                        console.log('update error: ' + updResponse.msg)
                        errorMessages.push(updResponse.msg);
                    }
                })
                .catch(error => {
                    console.log('update failure');
                    errorMessages.push(error);
                });
            } else {
                console.log('insert error.');
                errorMessages.push(response.msg);
            }
        }
    })
    .catch(error => {
        console.log('insert failure.');
        errorMessages.push(error);
    });
}

你能试试这个吗

for (let i = 0; i < expectedRows; i++) {
    let row = myArray[i];
    customerCode = row['customer_code'];
    customerName = row['customer_name'];
    customerBalance = row['customer_balance'];
    // Build body call
    let callBody = {
        user: 'USER',
        code: customerCode,
        name: customerName,
        balance: customerBalance
    };
    let fetchOptions = {
        method: "POST",
        cache: "no-cache",
        headers: {
            "Content-Type": "application/x-www-form-urlencoded",
        },
        redirect: "error",
        referrer: "ux-import", 
        body: JSON.stringify(callBody),
    };
    // Call
    let epurl = baseEP + '/customer/create';
    fetch(epurl, fetchOptions)
    .then(response => response.json())
    .then(response => {
        console.log(this) // <== Window object reference
        if (response.error === 0) {
            console.log('insert ok');
            insertRows++;
        } else {
            if (response.error == 2) {
                console.log('insert error => update');
                let updateEP = baseEP + '/customer/update';
                fetch(updateEP, fetchOptions) // <== Not what you expect 
                .then(updResponse => updResponse.json())
                .then(updResponse => {
                    if (updResponse.error === 0) {
                        console.log('update ok.')
                        updateRows++;
                    } else {
                        console.log('update error: ' + updResponse.msg)
                        errorMessages.push(updResponse.msg);
                    }
                })
                .catch(error => {
                    console.log('update failure');
                    errorMessages.push(error);
                });
            } else {
                console.log('insert error.');
                errorMessages.push(response.msg);
            }
        }
    })
    .catch(error => {
        console.log('insert failure.');
        errorMessages.push(error);
    });
}

for（设i=0；iresponse.json（））
。然后（响应=>{
console.log（this）//{
if（updResponse.error==0）{
console.log（'更新确定'）
updateRows++；
}否则{
console.log（'更新错误：'+updResponse.msg）
errorMessages.push（updResponse.msg）；
}
})
.catch（错误=>{
console.log（“更新失败”）；
错误消息。推送（错误）；
});
}否则{
log（'insert error'）；
errorMessages.push（response.msg）；
}
}
})
.catch（错误=>{
log（'insert failure'）；
错误消息。推送（错误）；
});
}

基本上，用

var

定义变量不是一个好方法，因为它不会在循环的每次迭代中保持其状态。但是使用

let

可以为每次迭代维护变量状态，即使在您的案例中执行了一些异步任务（如

fetch

）之后，也可以使用变量

for (let i = 0; i < expectedRows; i++) {
    let row = myArray[i];
    customerCode = row['customer_code'];
    customerName = row['customer_name'];
    customerBalance = row['customer_balance'];
    // Build body call
    let callBody = {
        user: 'USER',
        code: customerCode,
        name: customerName,
        balance: customerBalance
    };
    let fetchOptions = {
        method: "POST",
        cache: "no-cache",
        headers: {
            "Content-Type": "application/x-www-form-urlencoded",
        },
        redirect: "error",
        referrer: "ux-import", 
        body: JSON.stringify(callBody),
    };
    // Call
    let epurl = baseEP + '/customer/create';
    fetch(epurl, fetchOptions)
    .then(response => response.json())
    .then(response => {
        console.log(this) // <== Window object reference
        if (response.error === 0) {
            console.log('insert ok');
            insertRows++;
        } else {
            if (response.error == 2) {
                console.log('insert error => update');
                let updateEP = baseEP + '/customer/update';
                fetch(updateEP, fetchOptions) // <== Not what you expect 
                .then(updResponse => updResponse.json())
                .then(updResponse => {
                    if (updResponse.error === 0) {
                        console.log('update ok.')
                        updateRows++;
                    } else {
                        console.log('update error: ' + updResponse.msg)
                        errorMessages.push(updResponse.msg);
                    }
                })
                .catch(error => {
                    console.log('update failure');
                    errorMessages.push(error);
                });
            } else {
                console.log('insert error.');
                errorMessages.push(response.msg);
            }
        }
    })
    .catch(error => {
        console.log('insert failure.');
        errorMessages.push(error);
    });
}