Such as: function getValue(condition) = node console.log(localType) // 'Identifier' console. Since the LET declaration is not promoted to the top of the current code block, you need to manually place the let declaration at the top to make variables available within the entire code block. Inside a code block (enclosed by a pair of curly braces) Let the statementThe let declaration limits the scope of the variable to the current code block.Block-level scopes (also known as lexical scopes) are created when: In 2015 they released a new version of that specification, officially known as 'ECMAScript 2015,' but many developers refer to it by the working. Block-level statementīlock-level declarations make declared variables inaccessible outside the scope of the specified block. The official name of the JavaScript language is actually 'ECMAScript' because the committee that defines the language specification is part of the European Computer Manufacturers Association (ECMA). ES6 introduces block-level scopes to make the life cycle of variables more manageable. This is called variable ascending (or reactive). This way of declaring a variable is treated as if it were declared at the top of the function (or at the top of the global scope if the declaration is not in any function), regardless of where it is actually declared.

Block-level scopeīefore ES6, JS had only one way to declare variables - variables declared using the var keyword. Some of the new features commonly used in real-world development are summarized here. I also recently spent some time looking at Understanding Cript6 as a Chinese ebook. Javascript The front end api ECMAScript 6ĮS6 is now used extensively in many projects.

Ecmascript 6