JavaScript Use Strict
JavaScript Use Strict
"use strict" is a string that makes your program or function follow a strict operating context.
It means, the errors which were being ignored by the compiler, will now throw exception messages.
The purpose of "use strict" is to indicate that the code should be executed in "strict mode".
Advantage of using use strict
The following are the three main advantage of using use strict
- Prohibits some syntax likely to be defined in future versions of ECMAScript.
- Fixes mistakes that make it difficult for JavaScript engines to perform optimizations.
- Eliminates some JavaScript silent errors by changing them to throw errors.
Initialize Undeclared Variable
In strict mode, you cannot initialize a value to undeclared variables.
Example
Delete Variable
The strict mode will throw an error when you are trying to delete a variable instead of deleting a property of an object.
Example
Duplicate parameter
Duplicating parameter name is not allowed in strict mode.
Example
Octal literals
Octal literals are not allowed in strict mode.
Example
Octal Escape Sequences
Octal escape sequences are not allowed in strict mode.
Example
Read Only Object
Read only object properties are not allowed to change its value in strict mode.
Example
eval() Function
eval() is not allowed to create variables in the scope under Strict Mode.
Example
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