Each value can only occur once in a Set. A JavaScript Set is a collection of unique values. A Map has a property that represents the size of the map. A Map remembers the original insertion order of the keys. A Map holds key-value pairs where the keys can be any data type. When just returning a value, you can use the following shortcut: When having exactly one argument, you may omit the parentheses: When having no arguments, you have to use empty parentheses in the function declaration: Besides a shorter syntax, they offer advantages when it comes to keeping the scope of the keyword.Īrrow function syntax may look strange but it’s actually simple. This is a different way of creating functions in JavaScript. The const keyword allows you to declare a constant (a JavaScript variable with a constant value).Ĭonstants are similar to let variables, except that the value cannot be changed.Īrrow functions allows a short syntax for writing function expressions. You use let instead of var, const instead of var if you plan on never re-assigning this “variable”. The let keyword allows you to declare a variable with block scope. New built in methods for various classes. Languages like JavaScript, Jscript and ActionScript are governed by this specification. The specification is influenced by programming languages like Self, Perl, Python, and Java etc. It is used by applications to enable client-side scripting. 
What is ECMAScript?ĮCMAScript (ES) is a scripting language specification standardized by ECMAScript International. It was initially created to standardize JavaScript, which is the most popular implementation of ECMAScript. European Computer Manufacturers Association (ECMAScript) or (ES) is a standard for scripting languages like JavaScript, ActionScript and JScript.
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