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1.JavaScript-导入导出。
JS提供的导入导出机制，可以实现按需导入。
（1）按需导入
showMessage.js：
//简单的展示信息
export function simpleMessage(msg){console.log(msg)
}//复杂的展示信息
export function complexMessage(msg){console.log(new Date()+": "+msg)
}message.html：
<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>js导入导出</title>
</head><body><div id="app"><button id="btn">点我展示信息</button></div><script type="module">import {complexMessage} from './showMessage.js';document.getElementById("btn").onclick=function(){complexMessage('我被点击了...');}</script>z</body></html>运行结果：
（2）批量导出
showMessage.js：
//简单的展示信息
/* export */ function simpleMessage(msg){console.log(msg)
}//复杂的展示信息
/* export */ function complexMessage(msg){console.log(new Date()+": "+msg)
}export {complexMessage,simpleMessage} 导入和导出的时候,可以使用 as 重命名：
import {complexMessage as cm} from './showMessage.js';（3）默认的导出方式
//默认导出
export default{complexMessage,simpleMessage} <!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>js导入导出</title>
</head><body><div id="app"><button id="btn">点我展示信息</button></div><script type="module">// import {complexMessage as cm} from './showMessage.js';import messageMethods from './showMessage.js';document.getElementById("btn").onclick=function(){messageMethods.complexMessage('我被点击了...');}</script>z</body></html>