What is meant by strict mode in JavaScript and characteristics of JavaScript strict-mode?

In JavaScript, strict mode is a feature that allows developers to place their code into a stricter operating context, which helps prevent certain coding mistakes and makes the code more secure. When strict mode is enabled, the JavaScript interpreter will enforce a stricter set of rules and throw more errors when potential issues arise.

Some of the key characteristics of JavaScript strict mode include:

  1. Variable declarations: In strict mode, all variables must be declared with a var, let, or const keyword. This helps prevent issues with undeclared variables and variable hoisting.
  2. No implicit globals: In strict mode, undeclared variables are not automatically created as global variables. This helps prevent unintentional global variable creation.
  3. More restrictive function calls: In strict mode, the “this” keyword inside a function will not refer to the global object, as it would in non-strict mode. Additionally, strict mode requires that functions be called with the correct number of arguments.
  4. Eliminating some silent errors: In strict mode, certain types of errors that would have been ignored or handled silently in non-strict mode will instead throw an error. This can help developers catch potential issues earlier.
  5. More secure: Strict mode helps prevent certain types of code injection attacks by disallowing the use of the “eval” function to execute arbitrary code.

Overall, strict mode is a useful tool for ensuring that your JavaScript code is written in a consistent, secure, and error-free manner.