Express中将Angular通过FormData发送的JSON字符串转为对象的方法

Alright, let's break down what's happening here and how to fix it. The issue is that your JSON string is getting HTML-escaped when it hits your Express backend—those " values are just escaped double quotes. That's why JSON.parse() fails, even though console.dir() makes it look like valid data (console methods often auto-decode these entities for readability).

Step 1: Decode the HTML Entities First #

Before you can parse the JSON, you need to convert those " back into regular double quotes. You have two easy options:

Option A: Use a Reliable HTML Decoding Library

The he library is a popular, lightweight choice for handling HTML entity decoding.

1. Install it via npm:

   npm install he
   

2. Use it in your Express route:

   const he = require('he');
   
   // Inside your route handler
   const encodedData = req.body.data;
   const decodedData = he.decode(encodedData);
   const parsedCollections = JSON.parse(decodedData);
   
   // Now parsedCollections is your original array of objects, ready to use!
   console.log(parsedCollections[0].description); // Should log "store"
   

Option B: Quick Manual Replacement (For Simple Cases)

If you don't want to add a new dependency, you can write a quick replacement function for the specific escaped character you're seeing:

function decodeQuotes(str) {
  return str.replace(/"/g, '"');
}

// Inside your route handler
const encodedData = req.body.data;
const decodedData = decodeQuotes(encodedData);
const parsedCollections = JSON.parse(decodedData);

Why This Happens #

When you send FormData, Express typically uses the urlencoded parser from body-parser (or the built-in express.urlencoded() middleware). This parser automatically escapes HTML-special characters (like quotes) to prevent XSS vulnerabilities, which is why your JSON string gets mangled into " instead of ".

Bonus: Verify Your Backend Middleware Setup #

Make sure you have the urlencoded middleware configured correctly in your Express app. It should look something like this:

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

// This ensures FormData is parsed correctly
app.use(express.urlencoded({ extended: true }));

内容的提问来源于stack exchange，提问作者Prachi Sharma