What is the difference between JavaScript strict mode and non-strict mode?

What is the difference between JavaScript strict mode and non-strict mode?

JavaScript strict mode is a way to opt in to a restricted variant of JavaScript, which helps catch common coding errors and unsafe actions. Non-strict mode allows for more flexibility but can lead to bugs.

Can you give me examples of how strict mode changes behavior?

Sure! In strict mode, assigning a value to an undeclared variable will throw an error, while in non-strict mode, it will create a global variable.

Are there any performance differences between the two modes?

Generally, strict mode can lead to better performance optimizations by the JavaScript engine, but the difference is often negligible in most applications.

When should I use strict mode?

It's a good practice to use strict mode in your JavaScript code to avoid common pitfalls and improve code quality.