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来自 url 中的 query 参数可直接通过 context.query 获取，但 POST 方式提交的表单数据则需要借助中间件的解析来完成，比如 koa-bodyparser。
首先准备好一个表单页面，为了演示，其中包含一个数组类型的数据。
index.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="X-UA-Compatible" content="ie=edge" />
<title>post json</title>
</head>
<body>
<form action="/save" method="POST">
<div>
<label for="name"
>name:
<input type="text" name="name" id="name" value="Tom" />
</label>
</div>
<div>
<label for="age"
>age:
<input type="number" name="age" id="age" value="19" />
</label>
</div>
<div>
<label
>hobbies:
<br />
<input
type="text"
name="hobbies[0]"
id="hobbies[0]"
value="reading"
/>
<br />
<input type="text" name="hobbies[1]" id="hobbies[1]" value="music" />
<br />
<input type="text" name="hobbies[2]" id="hobbies[2]" value="swim" />
</label>
</div>
<button type="submit">Submit</button>
</form>
</body>
</html>
server.js
var Koa = require("koa");
var Router = require("koa-router");
var fs = require("fs");
var bodyParser = require("koa-bodyparser");
var app = new Koa();
var router = new Router();
app.use(bodyParser());
router.get("/", async (ctx, next) => {
ctx.type = "html";
ctx.body = fs.createReadStream("index.html");
});
router.post("/save", async (ctx, next) => {
ctx.body = ctx.request.body;
});
app.use(router.routes()).use(router.allowedMethods());
app.listen(3000);
console.log("server started at http:localhost:3000");
通过 Node.js 调试模式启动服务可查看到接收到的数据，其中数据类型解析正常。
$ node --inspect-brk server.js
server started
接收到的表单数据
但其实前台页面提交的并不是 JSON 类型，这是 koa-bodyparse 解析后的结果。通过 Chrome Devtools 的网络面板可看到，真实的类型为 Request 中 Content-Type 字段，为 application/x-www-form-urlencoded。
表单提交时的请求类型为 `application/x-www-form-urlencoded`
原生的 HTML 表单 <form> 是没有 JSON 类型的，其总共有三种默认的格式，
application/x-www-form-urlencodedmultipart/form-datatext/plain
默认为 application/x-www-form-urlencoded，可通过 <form> 表单的 enctype 指定。
所以真正意义上以 JSON 格式提交，需要借助 JavaScript，真实场景下表单也大多会走代码提交而非原生 submit 类型的 <button>。
首页更新表单代码添加 onsubmit 方法：
- <form action="/save" method="POST">
+ <form action="/save" method="POST" onsubmit="submitForm(event)" id="myForm">
添加以下代码到页面以提交表单：
<script>
function submitForm(event) {
event.preventDefault();
var formData = new FormData(myForm);
let data = {};
for (var [key, value] of formData.entries()) {
if (key.startsWith("hobbies")) {
data["hobbies"]
? data["hobbies"].push(value)
: (data["hobbies"] = [value]);
} else {
data[key] = value;
}
}
<span class="pl-en">fetch</span>(<span class="pl-s"><span class="pl-pds">"</span>/save<span class="pl-pds">"</span></span>, {
method<span class="pl-k">:</span> <span class="pl-s"><span class="pl-pds">"</span>POST<span class="pl-pds">"</span></span>,
headers<span class="pl-k">:</span> {
<span class="pl-s"><span class="pl-pds">"</span>Content-Type<span class="pl-pds">"</span></span><span class="pl-k">:</span> <span class="pl-s"><span class="pl-pds">"</span>application/json<span class="pl-pds">"</span></span>
},
body<span class="pl-k">:</span> <span class="pl-c1">JSON</span>.<span class="pl-c1">stringify</span>(data)
})
.<span class="pl-c1">then</span>(<span class="pl-k">function</span>(<span class="pl-smi">response</span>) {
<span class="pl-k">return</span> <span class="pl-smi">response</span>.<span class="pl-en">json</span>();
})
.<span class="pl-c1">then</span>(<span class="pl-k">function</span>(<span class="pl-smi">response</span>) {
<span class="pl-en">console</span>.<span class="pl-c1">log</span>(response);
});
}
</script>
最后完整的后台与页面代码为：
server.js
var Koa = require("koa");
var Router = require("koa-router");
var fs = require("fs");
var bodyParser = require("koa-bodyparser");
var app = new Koa();
var router = new Router();
app.use(bodyParser());
router.get("/", async (ctx, next) => {
ctx.type = "html";
ctx.body = fs.createReadStream("index.html");
});
router.post("/save", async (ctx, next) => {
ctx.body = ctx.request.body;
});
app.use(router.routes()).use(router.allowedMethods());
app.listen(3000);
console.log("server started at http:localhost:3000");
index.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="X-UA-Compatible" content="ie=edge" />
<title>post json</title>
</head>
<body>
<form action="/save" method="POST" onsubmit="submitForm(event)" id="myForm">
<div>
<label for="name"
>name:
<input type="text" name="name" id="name" value="Tom" />
</label>
</div>
<div>
<label for="age"
>age:
<input type="number" name="age" id="age" value="19" />
</label>
</div>
<div>
<label
>hobbies:
<br />
<input
type="text"
name="hobbies[0]"
id="hobbies[0]"
value="reading"
/>
<br />
<input type="text" name="hobbies[1]" id="hobbies[1]" value="music" />
<br />
<input type="text" name="hobbies[2]" id="hobbies[2]" value="swim" />
</label>
</div>
<button type="submit">Submit</button>
</form>
<script>
function submitForm(event) {
event.preventDefault();
var formData = new FormData(myForm);
let data = {};
for (var [key, value] of formData.entries()) {
if (key.startsWith("hobbies")) {
data["hobbies"]
? data["hobbies"].push(value)
: (data["hobbies"] = [value]);
} else {
data[key] = value;
}
}
fetch("/save", {
method: "POST",
headers: {
"Content-Type": "application/json"
},
body: JSON.stringify(data)
})
.then(function(response) {
return response.json();
})
.then(function(response) {
console.log(response);
});
}
</script>
</body>
</html>
再次查看提交时的 Content-Type 及所提交的数据，已经是 JSON 格式了。
通过 fetch 提交 JSON 格式的表单数据
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