在 for...of 中没有变量声明在 .js 中有效但在 .mjs 中无效

Question

`index.js`


let rows = [{ location: 10 }, { location: 11 }, { location: 12 }];

for (row of rows) {
    console.log(row);
}

运行节点

$ node index.js
{ location: 10 }
{ location: 11 }
{ location: 12 }

但是为什么

`index.mjs`


let rows = [{ location: 10 }, { location: 11 }, { location: 12 }];

for (row of rows) {
    console.log(row);
}

运行节点

$ node index.mjs
file:///C:/Users/WF-SYS-19/Desktop/D/walkover/index.mjs:4
for (row of rows) {
     ^

ReferenceError: row is not defined
    at file:///C:/Users/WF-SYS-19/Desktop/D/walkover/index.mjs:4:6
←[90m    at ModuleJob.run (internal/modules/esm/module_job.js:152:23)←[39m    
←[90m    at async Loader.import (internal/modules/esm/loader.js:177:24)←[39m  
←[90m    at async Object.loadESM (internal/process/esm_loader.js:68:5)←[39m

.js 和 .mjs 都工作正常，如果 row 变量声明为 const、let 或 var.for...of

Answer 1

mjs默认使用严格模式，所以不允许隐式定义。在循环中声明它 for (let row of rows) { 以绕过它。

在 for...of 中没有变量声明在 .js 中有效但在 .mjs 中无效

without variable declaration in for...of is working in .js but not in .mjs

javascript

node.js

node-modules

`index.js`

`index.mjs`