\nIn JavaScript, arrays store a list of items. An item may be a primitive such as a string or number. An item may also be an object or another array. Indexing starts at 0.
\nArrays are objects. To determine if a variable is an array, use <\/p>\n
\n Object.prototype.toString.call(theArray) === '[object Array]' \n<\/code><\/pre>\n\nor the newer way of <\/p>\n
\n Array.isArray(theArray);\n<\/code><\/pre>\nSome of the more commonly used actions that may be performed on an array include:<\/p>\n
Initialize:<\/p>\n
\n let myArray = ['a', 'b', 'c'];\n<\/code><\/pre>\n\nArrays can be created by calling:<\/p>\n
\n let myArray2 = new Array('a', 'b', 'c');\n<\/code><\/pre>\n\nThe first way is much simpler, so there’s not really any reason to use this way.<\/p>\n
\nTo retrieve the number of items in the list, do the following:<\/p>\n
\n let count = myArray.length;\n<\/code><\/pre>\nIndividual items in an array may be accessed by it’s index. To access the first item, call <\/p>\n
\n let firstItem = myArray[0];\n<\/code><\/pre>\n\nTo access the last item, call<\/p>\n
\n let lastItem = myArray[myArray.length-1];\n<\/code><\/pre>\n\nAdd an item to the end of the list:<\/p>\n
\n myArray.push('d');\n<\/code><\/pre>\n\nAdd an item to the beginning of the list:<\/p>\n
\n myArray.unshift('d');\n<\/code><\/pre>\n\nRemove last item:<\/p>\n
\n myArray.pop();\n<\/code><\/pre>\n\nRemove first item:<\/p>\n
\n myArray.shift();\n<\/code><\/pre>\n\nGet the number of items in an array:<\/p>\n
\n let count = myArray.length();\n<\/code><\/pre>\n\nGet the index of an item in an array: Note: this returns -1 if the item is not found:<\/p>\n
\n let index = myArray.indexOf('b');\n<\/code><\/pre>\n\nReturn a certain range of items, based on index, from an array:<\/p>\n
\n let subset = myArray.slice(1, 2);\n<\/code><\/pre>\nI tend to use objects more than arrays, but one common way to use arrays is when extracting pieces of a string. A string, such as an id, may contain several pieces of information separated by a delimiter. For example, the following string could represent a date with a dash as the delimiter:<\/p>\n
01-20-2020<\/p>\n
The month, date and year could be extracted as follows:<\/p>\n
\n let dateStr = '01-20-2020';\n let datePieces = dateStr.split('-');\n console.log('Month: ' + datePieces[0]);\n console.log('Day: ' + datePieces[1]);\n console.log('Year: ' + datePieces[2]);\n<\/code><\/pre>\n\nAn array may store another array, creating a multidimensional array. For example:<\/p>\n
\n let array2d = [[0,0], [3,5]];\n<\/code><\/pre>\nArrays can be searched using the Array.prototype.find function. A callback function which defines the search criteria is passed into the find function. The result is then returned.
\nExample:<\/p>\n
\n function search (item) {\n return item === 'b';\n }\n let bElement = myArray.find(search); \n<\/code><\/pre>\nImplementation:<\/strong><\/p>\nInside the javascript_tutorial.js file created in the JavaScript set up tutorial<\/a>, add the following lines that are in bold:<\/p>\n\/\/ JavaScript Tutorial\n\n\/*\n* This file will add JavaScript\n* to a website.\n*\/\n\n(function() {\n let doc = document;\n \n let defaultLocation = [-86.7816, 36.1627]; \/\/ longitude, latitude\n <\/strong>\n})(); \n<\/pre>\nThe JavaScript tutorial series starts with this post<\/a>.<\/p>\n(paid links)
\nMore JavaScript<\/a><\/p>\n