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JavaScript Strict Mode

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Questions and Answers

What was the problem with implicit globals in JavaScript?

Implicit globals allowed JavaScript to create global variables even if they were not declared, leading to frustrating programming errors.

What is the purpose of strict mode in JavaScript?

The purpose of strict mode is to prevent implicit globals and other errors.

How do you enable strict mode in JavaScript?

You can enable strict mode by adding the string 'use strict' (with single or double quotes) on a line by itself before any other code.

What is the effect of using strict mode in global scope?

Using strict mode in global scope will enable strict mode for the entire script, which can affect other scripts combined with it. Signup and view all the answers

Why is it recommended to wrap code in an immediately invoked function when using strict mode?

Wrapping code in an immediately invoked function prevents strict mode from contaminating other scripts combined with it. Signup and view all the answers

What is the benefit of using a linter in addition to strict mode?

A linter can save you from many of the same problems as strict mode, and doubling up can't hurt. Signup and view all the answers

What is the importance of understanding scope in programming?

Understanding scope is an important part of learning any programming language. Signup and view all the answers

What is a recommended resource for learning more about strict mode?

The MDN article on strict mode. Signup and view all the answers

Study Notes

Strict Mode

Implicit globals in ES5 allowed JavaScript to assume undeclared variables as global, leading to errors.
Strict mode prevents implicit globals and is enabled with the string "use strict" on a line by itself.
If used in global scope, strict mode applies to the entire script, while in a function, it only applies to that function.
Enabling strict mode in global scope can affect other scripts, so it's generally inadvisable.
Wrapping code in an immediately invoked function can enable strict mode without affecting other scripts.

Benefits of Strict Mode

Strict mode is considered a good thing and can help prevent errors.
Linters can also help prevent errors, but using strict mode can provide extra protection.

Scope and Closures

Understanding scope is essential in programming languages.
The introduction of let brings JavaScript in line with other modern languages.
JavaScript is one of the first popular languages to support closures.
Closures are an important part of modern JavaScript development and have been used effectively by the JavaScript community.