The let statement works exactly as the var statement but with a big difference: let declarations are restricted to the enclosing scope and are only available from the point where the statement is located onwards. The behavior of these statements is much more in line with what other languages do. For big codebases variable hoisting can result in unexpected and sometimes suprising behavior.ĮCMAScript 2015 introduces two new ways of declaring variables: let and const. Variable declarations in many other popular languages are restricted to the lexical scope of the enclosing block, so newcomers to JavaScript may completely ignore the semantics of var. var declarations act as if the variables are declared at the top of the current execution context (function). Since its inception, JavaScript had one way of declaring variables using the var statement, which obeys the rules of variable hoisting. Rauschmayer's blog where you can find in-depth looks at ECMAScript 2015. Of course, acknowledgements would not be complete without a reference to Dr. Another great resource for those of you wishing to learn more is the Mozilla Developer Network. This rundown is based on the excellent work of Luke Hoban and his es6features GitHub repository. We will also show you how to set up a modern project with ECMAScript 2015 plus async/await support. We will make special emphasis on how these features can help in the development of ever bigger systems and how they compare to the old way of doing things. In this article we will go over the new features of JavaScript/ECMAScript 2015, a major update to the language.
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