The JavaScript You Wished You Knew
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The document summarizes a presentation about JavaScript fundamentals. It discusses the history and origins of JavaScript, key concepts like functions, this, closures, and array methods. It also outlines new features introduced in ES5 and ES6 like strict mode, map/filter/reduce, arrow functions, and array.from. The presentation aims to cover fundamental JavaScript concepts and features that developers may wish they knew.
The JavaScript You Wished You Knew
- 1. PeopleSpace 23 August 2016 The JavaScript You Wished You Knew
- 2. Troy Miles Troy Miles Speaker and author https:// therockncoder.com/ rockncoder@gmail.com @therockncoder
- 3. @therockncoder Please follow me on twitter
- 4. Have MEAN October October 15th & 16th MongoDB, Express.js, Angular, and Node Build a full stack site using the latest versions Only $195 http://peoplespace.us/javascript/
- 6. Agenda The big lie What is this? function, function, function call, apply, and bind high order functions closure splice vs slice strict mode map, filter, and reduce arrow functions array.from Summary
- 7. The big lie Brendan Eich was hired to create Scheme for the browser It was released in Sept. 1995 as LiveScript It was renamed JavaScript in Dec. 1995 At the time NetScape and Sun were partners Sun owned the trademark, JavaScript
- 8. (What is Scheme?) Scheme is a functional language in the LISP family Some of the features of JavaScript like high order functions and closures come from its Scheme mother
- 9. Bad math JavaScript doesn’t have multiple kinds of numbers This means we are vulnerable to some shortcomings of base-2 numbers
- 10. What is this? this is a keyword You can’t directly modify it It is the context in which the code is running (It was the dumbest possible name for a keyword)
- 12. The secret parameters Every function receives two secret parameters this - which points to the current context arguments - an array-like structure holding all of the passed parameters
- 13. Every function returns a value If a function lacks a return statement, the function returns “undefined” undefined is a primitive type in JavaScript It can be used to compare in strict equalities Better to use typeof since it won’t throw an error
- 14. 4 ways to invoke a function 1. As a function 2. As a method of an object 3. As a function constructor 4. Using call or apply
- 15. call, apply call and apply are very similar both allow you to set both of the secret parameters call accepts a list of parameters for the arguments apply takes an array for the arguments Remember: A is for array, arguments, & apply
- 16. bind Bind is weird It creates a new function based on an older one It permanently assigns a this to the new function Remember: it binds this to the the function
- 17. high order functions Functions are first class objects in JavaScript Any place you use a variable, you can substitute with a function You can pass functions to functions And return functions from functions
- 18. What is a closure? A closure is a function which remembers the environment in which it was created This is super-powerful and enables JavaScript to do things not possible in other language
- 19. ES3
- 20. splice vs. slice Both introduced in ES3(1999) The splice() method changes the content of an array by removing existing elements and/or adding new elements. The slice() method returns a shallow copy of a portion of an array into a new array object. splice is DESTRUCTIVE
- 21. arguments arguments is array-like since it has a length property but it is not an array because it doesn’t have any of the array methods to convert it to an array is easy
- 22. ES5
- 23. strict mode “use strict”; or ‘use strict’; Must be the first statement in a file or function Turns on “ES5” mode JavaScript becomes more strict
- 24. map, filter, reduce map - transform one array into another filter - checks every value of an array, creating a new array reduce - turns an array into a scalar value
- 25. array methods most array methods are passed the same three parameters, in the same order element - the current value index - the current array index array - the entire array
- 26. ES6 / ES2015
- 27. array.from Creates a new array from array like objects or iterators Can turn arguments, strings, and others into arrays Can generate arrays based on values passed in
- 28. arrow function a short form of the anonymous function Captures the this of its parent code Best for non-method code In short form, it does an implicit return In long form, you must include a return statement
- 30. The End