JavaScript Functions

What’s in it for you? What are JavaScript functions? Function expressions Function() constructor Self-invoking functions Functions as values Functions as objects Arrow functions Generator function Predefined functions

What are JavaScript functions? A function is a group of reusable code which can be called anywhere in your program This eliminates the need of writing the same code again and again It helps programmers write modular codes

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Function Expression A JavaScript function can also be defined using an expression A function expression can be stored in a variable:

The Function Constructor JavaScript functions are defined using the keyword function. Functions can also be defined using the built-in JavaScript function constructor called Function()

Self-Invoking functions A self-invoking expression is invoked (started) automatically, without being called Function expressions will execute automatically if the expression is followed by () You have to add parentheses around the function to indicate that it is a function expression

Functions as values In JavaScript, a function is a value, so we can deal with it as a value. We first define the function and then assign it to a variable unlike in expressions

Functions as objects JavaScript functions are a special type of objects, called function objects A function object includes a string which holds the actual code i.e., the function body of the function

Arrow functions Functions can be written more compactly with the help of Arrow functions Arrow function expressions are ill suited as methods, and they cannot be used as constructors The above code can be re-written like this

To create a generator, we need a special syntax construct: function*, so-called “generator function” Generator functions Regular functions return only one, single value (or nothing) Generators can return (“yield”) multiple values, one after another, on-demand To create a generator, we use the syntax: function*

To create a generator, we need a special syntax construct: function*, so-called “generator function” Generator functions Regular functions return only one, single value (or nothing) Generators can return (“yield”) multiple values, one after another, on-demand To create a generator, we use the syntax: function* next() returns two properties: value: The yielded value done: True if the function code is finished, false if otherwise

To create a generator, we need a special syntax construct: function*, so-called “generator function” Predefined functions eval Evaluates a string and returns a value parseInt Parses a string argument and returns an integer of the specified radix or base parseFloat Parses a string argument and returns a floating-point number escape Returns the hexadecimal encoding of an argument unescape Returns the ASCII string for the specified value

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