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Ways of Creating Functions in ECMAScript 2015

Functions in ECMAScript - Part 1

ECMAScript 6

Foreword: In this part of the series, I talk about different ways of creating functions in ECMAScript.

By: Chrysanthus Date Published: 25 May 2016

Ways of Creating Functions in ECMAScript 2015

This is part 1 of my series, Functions in ECMAScript. In this part of the series, I talk about different ways of creating functions in ECMAScript.

Pre-Knowledge
At the bottom of this page, you have links to the different series, you should have read before coming here, to better understand this one.

Function Declaration
The following is a function declaration:

        function fn (word1, word2)
            {
             str = word1 + " who laughs " + word2 + ", laughs best.";
             return str;
            }

It has the reserved word, function and the name of the function. Try the following code:

    <script type="text/ECMAScript">

        function fn (word1, word2)
            {
             str = word1 + " who laughs " + word2 + ", laughs best.";
             return str;
            }

        stri = fn('He','last');

     alert(stri);

    </script>

Function Expressions
The following is a function expression (anonymous):

        function (word1, word2)
            {
             str = word1 + " who laughs " + word2 + ", laughs best.";
             return str;
            }

This expression (structure) can be assigned to a variable. Try the following code:

        fn = function (word1, word2)
            {
             str = word1 + " who laughs " + word2 + ", laughs best.";
             return str;
            }

        stri = fn('He','last');

     alert(stri);

The following is a function expression (anonymous) without the reserved word, function, but with parameters and the arrow punctuator:

        (word1, word2) =>
            {
             str = word1 + " who laughs " + word2 + ", laughs best.";
             return str;
            }

This expression (structure) can be assigned to a variable. Try the following code:

        fn = (word1, word2) =>
            {
             str = word1 + " who laughs " + word2 + ", laughs best.";
             return str;
            }

        stri = fn('He','last');

     alert(stri);

The Function Property of the Global Object
There is an object called the global object in ECMAScript. This object has a property, which is:

    Function(. . .)

This is a constructor and can be used to create functions. In ECMAScript a function is an object. The syntax to use this property to create an object is:

    new Function ( p1, p2, , pn, body )

A function body (in curly braces, {}) is not really a property of a function. It is like a parameter to the function. Read and try the following code:

    <script type="text/ECMAScript">

        fn = new Function("word1",
                         "word2",
                         "str = word1 + \" who laughs \" + word2 + \", laughs best.\"; return str;");

        stri = fn('He','last');

     alert(stri);

    </script>

All the parameters in the parentheses are in quotes. The last quotation is the function body. Any quote in this body is escaped. There is no newline character in the body. The parameters are separated by commas.

You call the function returned by the constructor, in the same way as you call functions created in other ways.

That is it for this part of the series. We stop here and continue in the next part.

Chrys

Related Links

ECMAScript Basics
ECMAScript Operators
Expressions in ECMAScript
Statements in ECMAScript
Custom Objects in ECMAScript
Functions in ECMAScript
ECMAScript Date Object
The ECMAScript String Object
ECMAScript String Regular Expressions
ECMAScript Template Literal
The ECMAScript Array
ECMAScript Sets and Maps
ECMAScript Number
Scopes in ECMAScript
Mastering the ECMAScript (JavaScript) eval Function
Sending Email with ECMAScript
ECMAScript Insecurities and Prevention
Advanced Course
Advanced ECMAScript Regular Expressions
Promise in ECMAScript 2015
Generator in ECMAScript 2015
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