In this chapter we would cover Data Types and Variables.<\/p>\n
We would cover the following:<\/p>\n
<\/p>\n
JavaScript supports three types of primitive data types: Numbers, Strings and Boolean<\/p>\n
<\/p>\n
Numbers<\/strong>: These are numeric values. For example 100, 34, 12,5. Note that JavaScript does not differentiate between integer and floating point data. All are represented as floating-points. The size is 64 bits<\/p>\n Strings<\/strong>: Used for text data. For example: “Learn JavaScript”, “My name is Kindson”<\/p>\n Boolean<\/strong>: This is data type for True or False values<\/p>\n <\/p>\n There is also two trivial data types: null and undefined. We would use these more in later sections.<\/p>\n <\/p>\n Composite Data<\/strong><\/p>\n JavaScript also supports composite data type. This is made up of combination of two or more primitive types. The composite data type is called object.<\/p>\n <\/p>\n <\/p>\n You probably have heard of variables. All programming languages use variables. A variable is like a container to hold data. Hence you can assign values to variables. However before you can use a variable, you must declare it.<\/p>\n To declare a variable, you use the var<\/strong> keyword. The code below declare three variables.<\/p>\n <\/p>\n <\/p>\n After you declare a variable, then you can assign a value to the variable. This is called initialization<\/strong>. A variable can also be initialized the same time it it declared. For example, the code below declares the variables and assigns them at the same time.<\/p>\n <\/p>\n <\/p>\n <\/p>\n Also note that JavaScript is an untyped language. This means that variables are not tied to any specific type. Therefore a particular variable can hold any type: be it a number, string or boolean. Again, a variable can start off with holding a String value and then later you can assign it a number.<\/p>\n <\/p>\n <\/p>\n The concept of variable scope actually applies across programming languages.<\/p>\n So, what is a variable scope?<\/strong><\/p>\n A variable scope is\u00a0 the block of code where a variable is defined. There are two variable types of variable scopes in JavaScript: Local and Global.<\/p>\n <\/p>\n Local Variable<\/strong>: A local variables is a variable that is only visible within the function where it is defined. Function parameters for example. Hence, local variables are not visible outside the block<\/p>\n Global Variable:<\/strong> A global variable is a variable that is available anywhere in the JavaScript program. Both inside and outside functions<\/p>\n <\/p>\n Inside the body of a function, local variables take precedence over global variables. These means that if there is a global variable with the same name, then the local variable is used. Let’s take an example:<\/p>\n <\/p>\n <\/p>\n <\/p>\n In the above code, when you run this page, then “local variable” is displayed. This is because, the write statement was done inside the function.<\/p>\n <\/p>\n You can choose names for variables in JavaScript. However, the following rules apply to naming variables:<\/p>\n a. Any of the JavaScript reserved words cannot be used as a variable name. Reserved words are also known as keywords and a list of them is given below.<\/p>\n b. Variable names must not start with a number eg 0-9. Variable names must begin with a letter or an underscore. For instance score32, _firstname, address.<\/p>\n c. Variable names in JavaScript are case-sensitive. Therefore the variable Score is not the same as score.<\/p>\n <\/p>\n List of JavaScript Reserved Words<\/strong><\/p>\n The table below provides a list of all JavaScript keywords.<\/p>\n <\/p>\n In this chapter we would cover Data Types and Variables. We would cover the following: JavaScript Data Types Variables in JavaScript Variable Scope Variable Names … <\/p>\n","protected":false},"author":395,"featured_media":27,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"footnotes":""},"categories":[2],"tags":[],"class_list":["post-23","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-javascript-tutorials"],"_links":{"self":[{"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/posts\/23","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/users\/395"}],"replies":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/comments?post=23"}],"version-history":[{"count":3,"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/posts\/23\/revisions"}],"predecessor-version":[{"id":39,"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/posts\/23\/revisions\/39"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/media\/27"}],"wp:attachment":[{"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/media?parent=23"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/categories?post=23"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kindsonthegenius.com\/javascript\/wp-json\/wp\/v2\/tags?post=23"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}2. Variables in JavaScript<\/strong><\/h4>\n
<<\/span>script type =<\/span> \"text\/javascript\"<\/span>><\/span>\r\n var<\/span> score;\r\n var<\/span> name;\r\n var<\/span> address;\r\n<<\/span>\/script>\r\n<\/pre>\n<<\/span>script type =<\/span> \"text\/javascript\"<\/span>><\/span>\r\n var<\/span> score =<\/span> 58.7<\/span>;\r\n var<\/span> name \"Solace Okeke\"<\/span>;\r\n var<\/span> address =<\/span> \"No 34 King Will Avenue\"<\/span>;\r\n<<\/span>\/script>\r\n<\/pre>\n3. Variable Scope in JavaScript<\/strong><\/h4>\n
<html><\/span>\r\n<head><\/span>\r\n<title><\/span> Variable Scopes<\/title><\/span>\r\n<\/head><\/span>\r\n <body<\/span> onload =<\/span> vascope();<\/span>><\/span> \r\n <script <\/span>type =<\/span> \"text\/javascript\"<\/span>><\/span>\r\n <!--<\/span>\r\n\t\t \r\n\t \/\/ Global variable<\/span>\r\n var<\/span> variable1 =<\/span> \"global variable\"<\/span>; \r\n\t\t\t\r\n function<\/span> vascope( ) {\r\n\t\t\t\r\n\t \/\/ Local variable<\/span>\r\n var<\/span> variable1 =<\/span> \"local variable\"<\/span>;\r\n document<\/span>.write(variable1);\r\n }\r\n \/\/--><\/span>\r\n <\/script><\/span> \r\n <\/body><\/span>\r\n<\/html><\/span>\r\n<\/pre>\n<\/h4>\n
4. Variable Names in JavaScript<\/strong><\/h4>\n
\n\n
\n abstract<\/td>\n else<\/td>\n instanceof<\/td>\n switch<\/td>\n<\/tr>\n \n boolean<\/td>\n enum<\/td>\n int<\/td>\n synchronized<\/td>\n<\/tr>\n \n break<\/td>\n export<\/td>\n interface<\/td>\n this<\/td>\n<\/tr>\n \n byte<\/td>\n extends<\/td>\n long<\/td>\n throw<\/td>\n<\/tr>\n \n case<\/td>\n false<\/td>\n native<\/td>\n throws<\/td>\n<\/tr>\n \n catch<\/td>\n final<\/td>\n new<\/td>\n transient<\/td>\n<\/tr>\n \n char<\/td>\n finally<\/td>\n null<\/td>\n true<\/td>\n<\/tr>\n \n class<\/td>\n float<\/td>\n package<\/td>\n try<\/td>\n<\/tr>\n \n const<\/td>\n for<\/td>\n private<\/td>\n typeof<\/td>\n<\/tr>\n \n continue<\/td>\n function<\/td>\n protected<\/td>\n var<\/td>\n<\/tr>\n \n debugger<\/td>\n goto<\/td>\n public<\/td>\n void<\/td>\n<\/tr>\n \n default<\/td>\n if<\/td>\n return<\/td>\n volatile<\/td>\n<\/tr>\n \n delete<\/td>\n implements<\/td>\n short<\/td>\n while<\/td>\n<\/tr>\n \n do<\/td>\n import<\/td>\n static<\/td>\n with<\/td>\n<\/tr>\n \n double<\/td>\n in<\/td>\n super<\/td>\n <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"excerpt":{"rendered":"