with

JavaScript with Keyword Examples

The with statement, which runs only in sloppy mode, adds an object’s properties to the scope of a block:

> const point = { x: 3, y: 4 };
undefined
> with (point) {
…   Math.sqrt(x * x + y * y);
… }
5

Inside the block, x and y resolve to point.x and point.y. The same statement in an ES module fails before any code runs:

with (Math) {
  console.log(PI);
}

Node.js reports the error when it loads the module:

$ node legacy.mjs
SyntaxError: Strict mode code may not include a with statement

With import attributes, a module can import this settings.json file:

{ "theme": "dark", "fontSize": 14 }

The type: "json" attribute makes Node.js parse the file as JSON, and the parsed object becomes the default export:

import settings from "./settings.json" with { type: "json" };

console.log(`Theme: ${settings.theme}`);
console.log(`Font size: ${settings.fontSize}`);

Running theme.mjs prints both settings:

$ node theme.mjs
Theme: dark
Font size: 14

Without the attribute, Node.js throws a TypeError. Dynamic import() takes the attributes as a with option.

JavaScript with Keyword Use Cases

• Importing JSON files as modules with { type: "json" }
• Loading JSON data through dynamic import() with the with option
• Recognizing the legacy with statement in old sloppy-mode scripts