To expand: use strict is always in force in ES6.

gsnedders · on June 27, 2017

In ES6 modules, it is. In other code, ES6 is backwards compatible with ES5 (i.e., code is strict mode iff there's a "strict mode" declaration).

paulddraper · on June 27, 2017

Oops. Left off that key word :) Yes, ES6 modules.

nailer · on June 27, 2017

That's not correct: a small percentage of the JS community (maybe <1%) use TC39 modules (which enforce strict mode) vs just using npm.

paulddraper · on June 29, 2017

I am correct because I'm talking about ECMAScript 6. http://www.ecma-international.org/ecma-262/6.0/

If you're talking about Node.js or JScript or something else, then that's different.

lexicality · on June 28, 2017

In node perhaps.

They're extremely common in the front end world - all the fancy SPA frameworks and build systems promote & use them extensively.