What is "export default" in JavaScript?

File: SafeString.js

// Build out our basic SafeString type
function SafeString(string) {
  this.string = string;
}

SafeString.prototype.toString = function() {
  return "" + this.string;
};

export default SafeString;

I have never seen export default before. Are there any equivalent stuff for export default that can be easier to understand?

It's part of the ES6 module system, described here. There is a helpful example in that documentation, also:

If a module defines a default export:

// foo.js
export default function() { console.log("hello!") }

then you can import that default export by omitting the curly braces:

import foo from "foo";
foo(); // hello!

Update: As of June 2015, the module system is defined in §15.2 and the export syntax in particular is defined in §15.2.3 of the ECMAScript 2015 specification.

Stack Overflow Q#21117160, score: 708