Arrow Functions in ECMAscript 2015

Functions in ECMAScript - Part 2

ECMAScript 6

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

By: Chrysanthus Date Published: 25 May 2016

Introduction

This is part 2 of my series, Functions in ECMAScript. In this part of the series, I talk about arrow functions in ECMAScript. An arrow function is a function expression, which typically does not have a name or the reserved word, function. It can be assigned to a variable. Between the parameters group (list) and the function body, is the punctuator, => .

Illustration
The following has a function expression assigned to the variable, fn:

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

        stri = fn('He','last');

       alert(stri);

If there is only one parameter, then parentheses for the parameter group is optional Try the following code:

    <script type="text/ECMAScript">

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

        stri = fn('He','last');

       alert(stri);

    </script>

A function with no parameters still requires parentheses. Try the following code:

        fn = () =>
            {
               str = "He who laughs last, laughs best.";
               return str;
            }

        stri = fn('He','last');

       alert(stri);

If there is only one statement, then there is no need for the block (curly brackets). The result of the statement is returned. Try the following code:

        fn = () =>
         "He who laughs last, laughs best.";

        stri = fn('He');

       alert(stri);

Default parameters are supported. Try the following code:

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

        stri = fn('He');

       alert(stri);

Destructuring within the parameter list is also supported. In the following code, each parameter is an expression resulting in a value. The values passed to the function body are 1, 2 and 3, for a, b, and c respectively. The parameters are separated by commas.

        fn = ([a, b] = [1, 2], {x: c} = {x: a + b}) => a + b + c;

        ret = fn();

        alert(ret);

The display (output) is 6.

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

Chrys

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