Question

当JSON.parse（）失败时，应该捕获它，res.end（）应该终止客户端请求。但for循环仍以某种方式执行，导致TypeError。为什么会达到这一点？它好像try-catch块是异步的，因此标题。

const express = require('express');
const http = require('http');

app.get('/', (req, res) => {

    var options = {
        host: 'www.example.com'
    };

    var i = 0
    while (i < 5){
        i++;
        http.get(options, function(resp) {
            var body = '';
            resp.on('data', function(chunk) {
                body += chunk;
            });

            resp.on('end', function() {

                try{
                    var j = JSON.parse(body); // Body will ocasionally be non-json
                }catch(e){
                    res.end("JSON couldn't parse body"); // This should terminate the main request
                }

                for(let item of j.list){
                    console.log(item); // This block sholdn't execute if try-catch fails
                }

            });
        });
    }

});

Answer 1

...

try{
  var j = JSON.parse(body); // Body will ocasionally be non-json
}catch(e){
    res.end("JSON couldn't parse body"); // This should terminate the main request
    return; // <<<<<
}

...

Answer 2

如果JSON.parse（body）抛出异常，你还需要捕获j.list的for循环的异常，把它放在try块中：

        resp.on('end', function() {

            try{
                var j = JSON.parse(body); // Body will ocasionally be non-json
                for(let item of j.list){
                    console.log(item); // This block sholdn't execute if try-catch fails
                }
            }catch(e){
                res.end("JSON couldn't parse body"); // This should terminate the main request
            }


        });

NodeJS Try-Catch没有阻塞

2 个答案: