I have started to explore the Node.js and wrote many demo web application, to understand the flow of Node.js, Express.js, jade, etc..
But one thing I came across recently, is the statement
"use strict" as the first line inside every function and every
How exactly is it is interpreted by Node.js?
Basically it enables the strict mode.
Strict Mode is a feature that allows you to place a program, or a function, in a "strict" operating context. In strict operating context, the method form binds this to the objects as before. The function form binds this to undefined, not the global set objects.
So, there will be no major difference how
"use strict"; is interpreted by the Chrome browser and Node.js.
For more information:
- Strict mode
- ECMAScript 5 Strict mode support in browsers
- Strict mode is coming to town
- Compatibility table for strict mode
ECMAScript 6 Code & strict mode. Following is brief from the specification:
10.2.1 Strict Mode Code
An ECMAScript Script syntactic unit may be processed using either unrestricted or strict mode syntax and semantics. Code is interpreted as strict mode code in the following situations:
- Global code is strict mode code if it begins with a Directive Prologue that contains a Use Strict Directive (see 14.1.1).
- Module code is always strict mode code.
- All parts of a ClassDeclaration or a ClassExpression are strict mode code.
- Eval code is strict mode code if it begins with a Directive Prologue that contains a Use Strict Directive or if the call to eval is a direct eval (see 188.8.131.52) that is contained in strict mode code.
- Function code is strict mode code if the associated FunctionDeclaration, FunctionExpression, GeneratorDeclaration, GeneratorExpression, MethodDefinition, or ArrowFunction is contained in strict mode code or if the code that produces the value of the function’s [[ECMAScriptCode]] internal slot begins with a Directive Prologue that contains a Use Strict Directive.
- Function code that is supplied as the arguments to the built-in Function and Generator constructors is strict mode code if the last argument is a String that when processed is a FunctionBody that begins with a Directive Prologue that contains a Use Strict Directive.
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