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article/2021/importing-json-modules-in-typescript.md

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+> * 原文地址：[Importing JSON Modules in TypeScript](https://mariusschulz.com/blog/importing-json-modules-in-typescript)
+> * 原文作者：[Marius Schulz](https://mariusschulz.com/)
+> * 译文出自：[掘金翻译计划](https://github.com/xitu/gold-miner)
+> * 本文永久链接：[https://github.com/xitu/gold-miner/blob/master/article/2021/importing-json-modules-in-typescript.md](https://github.com/xitu/gold-miner/blob/master/article/2021/importing-json-modules-in-typescript.md)
+> * 译者：
+> * 校对者：
+
+# Importing JSON Modules in TypeScript
+
+TypeScript 2.9 introduced a new `--resolveJsonModule` compiler option that lets us import JSON modules from within TypeScript modules.
+
+## Importing JSON Modules via `require` Calls
+
+Let's assume we have a Node application written in TypeScript, and let's say that we want to import the following JSON file:
+
+```json
+{
+  "server": {
+    "nodePort": 8080
+  }
+}
+```
+
+In Node, we can use a `require` call to import this JSON file like any other CommonJS module:
+
+```js
+const config = require("./config.json");
+```
+
+The JSON is automatically deserialized into a plain JavaScript object. This allows us to easily access the properties of our config object:
+
+```js
+"use strict";
+
+const express = require("express");
+const config = require("./config.json");
+
+const app = express();
+
+app.listen(config.server.nodePort, () => {
+  console.log(`Listening on port ${config.server.nodePort} ...`);
+});
+```
+
+So far, so good!
+
+## Importing JSON Files via Static `import` Declarations
+
+Let's now say we want to use native ECMAScript modules instead of CommonJS modules. This means we'll have to convert our `require` calls to static `import` declarations:
+
+```js
+// We no longer need the "use strict" directive since
+// all ECMAScript modules implicitly use strict mode.
+
+import * as express from "express";
+import * as config from "./config.json";
+
+const app = express();
+
+app.listen(config.server.nodePort, () => {
+  console.log(`Listening on port ${config.server.nodePort} ...`);
+});
+```
+
+Now, we get a type error in line 2. TypeScript doesn't let us import a JSON module out of the box, just like that. This was a conscious design decision made by the TypeScript team: pulling in large JSON files could potentially [consume a lot of memory](https://github.com/Microsoft/TypeScript/pull/22167#issuecomment-385479553), which is why we need to opt into that feature by enabling the `--resolveJsonModule` compiler flag:
+
+> Having people to consciously opt into this would imply the user understands the cost.
+
+Let's head over to our **tsconfig.json** file and enable the `resolveJsonModule` option there:
+
+```json
+{
+  "compilerOptions": {
+    "target": "es2015",
+    "module": "commonjs",
+    "strict": true,
+    "moduleResolution": "node",
+    "resolveJsonModule": true
+  }
+}
+```
+
+With `--resolveJsonModule` enabled, we no longer get a type error in our TypeScript file. Even better, we now get type checking and autocompletion!
+
+If we compile our TypeScript file with the compiler options shown above, we get the following JavaScript output:
+
+```js
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const express = require("express");
+const config = require("./config.json");
+const app = express();
+app.listen(config.server.nodePort, () => {
+    console.log(`Listening on port ${config.server.nodePort} ...`);
+});
+```
+
+Notice that the output is pretty much identical to our initial `require` version:
+
+```js
+"use strict";
+
+const express = require("express");
+const config = require("./config.json");
+
+const app = express();
+
+app.listen(config.server.nodePort, () => {
+  console.log(`Listening on port ${config.server.nodePort} ...`);
+});
+```
+
+And there you go! This is how to import JSON modules from within TypeScript modules, only one compiler option away.
+
+> 如果发现译文存在错误或其他需要改进的地方，欢迎到 [掘金翻译计划](https://github.com/xitu/gold-miner) 对译文进行修改并 PR，也可获得相应奖励积分。文章开头的 **本文永久链接** 即为本文在 GitHub 上的 MarkDown 链接。
+
+---
+
+> [掘金翻译计划](https://github.com/xitu/gold-miner) 是一个翻译优质互联网技术文章的社区，文章来源为 [掘金](https://juejin.im) 上的英文分享文章。内容覆盖 [Android](https://github.com/xitu/gold-miner#android)、[iOS](https://github.com/xitu/gold-miner#ios)、[前端](https://github.com/xitu/gold-miner#前端)、[后端](https://github.com/xitu/gold-miner#后端)、[区块链](https://github.com/xitu/gold-miner#区块链)、[产品](https://github.com/xitu/gold-miner#产品)、[设计](https://github.com/xitu/gold-miner#设计)、[人工智能](https://github.com/xitu/gold-miner#人工智能)等领域，想要查看更多优质译文请持续关注 [掘金翻译计划](https://github.com/xitu/gold-miner)、[官方微博](http://weibo.com/juejinfanyi)、[知乎专栏](https://zhuanlan.zhihu.com/juejinfanyi)。