3e:null 3f:["$","title",null,{"children":"Functional programming - Code samples | Peter Varholak | Observable"}] 45:[] 43:{"id":"582a481f7b26a149","slug":"functional-programming-code-samples","title":"Functional programming - Code samples","thumbnail":"4268483bb7b3d1e1eb1f618fe6eef2c9b3b6b3efc6f7cff3b4f9eea6357f3b4c","access_level":"public","create_time":"$D2019-04-16T09:41:56.200Z","update_time":"$D2019-04-16T17:09:23.669Z","view_time":null,"first_public_time":"$D2019-04-16T10:54:25.961Z","has_unpublished_edits":null,"fork":{"id":"32412ee9288d2a15","slug":"react-nights-playground","title":"Functional programming","owner":{"id":"5dcb3bb7054187b5","login":"varholak-peter","name":"Peter Varholak"}},"stars":1,"starred":false,"owner":{"type":"team","id":"5dcb3bb7054187b5","login":"varholak-peter","name":"Peter Varholak","avatar_url":"https://avatars-next.observableusercontent.com/772bcdd820800f5b68a0b965fc268ca80cc3e5cec34e34c14078e6db0b97ea75","tier":"starter_2024","bio":""},"version":560,"publish_version":560,"role":null,"authored":false,"authors":[{"type":"individual","id":"30a69b13a2c79642","login":"varholak-peter","name":"Peter Varholak","avatar_url":"https://avatars-next.observableusercontent.com/772bcdd820800f5b68a0b965fc268ca80cc3e5cec34e34c14078e6db0b97ea75","tier":null,"bio":""}],"members":[{"type":"individual","id":"30a69b13a2c79642","login":"varholak-peter","name":"Peter Varholak","avatar_url":"https://avatars-next.observableusercontent.com/772bcdd820800f5b68a0b965fc268ca80cc3e5cec34e34c14078e6db0b97ea75","tier":null,"role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":1,"collection":null,"type":"notebook","body":{"titling":"auto","title":"Functional programming - Code samples","cells":[{"id":79,"value":"md`\n# Functional programming - Code samples\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":99,"value":"md`\n## Purity\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":102,"value":"sum = (a, b) => a + b","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":108,"value":"sum(10, 2)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":311,"value":"md`\n## Immutability\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":330,"value":"oldArr = [1, 2, 3, 4]","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":337,"value":"oldObj = ({ id: 1, label: 'Kobzol', x: 'foo', y: 'bar', z: 'baz' })","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":372,"value":"md`\n#### Changing primitive variable\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":374,"value":"{\n // Not `x += 1` or `x++` (you would need to use \"let\" keyword anyway)\n const x = 1\n const x1 = x + 1\n return x1\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":327,"value":"md`\n#### Adding to an array\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":333,"value":"// Not `oldArr.push(5)`\n[...oldArr, 5]","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":349,"value":"md`\n#### Prepending to an array\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":350,"value":"// Not `oldArr.unshift(0)`\n[0, ...oldArr]","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":353,"value":"md`\n#### Adding property into an object\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":354,"value":"// Not `oldObj.new = 'quox'`\n({ ...oldObj, new: 'quox' })","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":366,"value":"md`\n#### Overwriting property in an object\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":368,"value":"// Not `oldObj.label = 'Potato'`\n({ ...oldObj, label: 'Potato' })","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":357,"value":"md`\n#### Removing property from an object\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":363,"value":"{\n // Not `delete oldObj.z`\n const { z, ...newObj } = oldObj\n return newObj\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":113,"value":"md`\n## Composability & Currying\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":125,"value":"subtract = (a, b) => a - b","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":128,"value":"multiply = (a, b) => a * b","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":131,"value":"divide = (a, b) => a / b","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":135,"value":"md`\nSanity check:\n- \\`10 - 2: ${subtract(10, 2)}\\`\n- \\`10 * 2: ${multiply(10, 2)}\\`\n- \\`10 / 2: ${divide(10, 2)}\\`\n`","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":142,"value":"pass10 = (fn, b) => fn(10, b)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":147,"value":"pass10(sum, 5)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":150,"value":"pass10(multiply, 5)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":158,"value":"pass10((a, b) => (20 + a) / b, 5)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":168,"value":"cSum = a => b => a + b","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":173,"value":"cSubtract = a => b => a - b","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":177,"value":"cMultiply = a => b => a * b","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":180,"value":"cDivide = a => b => a / b","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":185,"value":"cSum(10)(2)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":194,"value":"{\n const add5 = cSum(5)\n return [add5(5), add5(2), add5(100)]\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":217,"value":"md`\n## Data transformation\n\ntype Product {
\n  id: number;
\n  name: string;
\n  sex: \"F\" | \"M\";
\n  size: \"L\" | \"M\" | \"S\";
\n  type: \"pants\" | \"shirt\"
\n}\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":224,"value":"{\n let mediumProducts = []\n for (let i = 0; i < products.length; i++) {\n let currentProduct = products[i]\n if (currentProduct.size === \"M\") {\n mediumProducts.push(currentProduct)\n }\n }\n return mediumProducts\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":232,"value":"products.filter(product => product.size === \"M\")","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":243,"value":"isMedium = product => product.size === \"M\"","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":246,"value":"products.filter(isMedium)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":259,"value":"getProductName = product => product.name","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":264,"value":"products.map(getProductName)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":283,"value":"getName = ({ name }) => name","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":295,"value":"products.map(getName)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":303,"value":"md`\ntype Customer {
\n  id: number;
\n  name: string;
\n  sex: \"F\" | \"M\";
\n  size: \"L\" | \"M\" | \"S\";
\n}\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":307,"value":"customers.map(getName)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":497,"value":"md`\nLet's say that our task for now is creating an object which has product ids as keys and the value for each key will be the name of the product, but this time composed of \\`sex\\`, \\`size\\` & \\`type\\` properties:\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":502,"value":"products.reduce((acc, { id, sex, size, type }) => ({\n ...acc,\n [id]: `${type} - ${sex} (${size})`\n}), {})","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":401,"value":"md`\n## Ramda\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":407,"value":"rGetName = R.prop('name')","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":413,"value":"R.map(rGetName, customers)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":421,"value":"md`\n### Imperative example\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":424,"value":"{\n let output = {}\n \n for (let i = 0; i < customers.length; i++) {\n const { name: cName, sex: cSex, size: cSize } = customers[i]\n \n let productNames = []\n \n for (let j = 0; j < products.length; j++) {\n const { name: pName, sex: pSex, size: pSize } = products[j]\n \n if (cSex === pSex && cSize === pSize) {\n productNames.push(pName)\n }\n }\n \n output[cName.toUpperCase()] = productNames\n }\n \n return output\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":436,"value":"md`\n### Functional example\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":437,"value":"customers.reduce((acc, { name: cName, sex: cSex, size: cSize }) => {\n const productNames = products\n .filter(\n ({ sex: pSex, size: pSize }) => cSex === pSex && cSize === pSize\n )\n .map(R.prop('name'))\n\n return {\n ...acc,\n [R.toUpper(cName)]: productNames\n }\n }, {})","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":465,"value":"md`\n### Ramda example\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":450,"value":"{\n const extractSexSize = R.pick(['sex', 'size'])\n const isSameSexSize = obj1 => obj2 => R.equals(extractSexSize(obj1), extractSexSize(obj2))\n const filterProducts = nProducts => nCustomer => R.filter(isSameSexSize(nCustomer), nProducts)\n const getName = R.prop('name')\n const getUpperName = R.pipe(getName, R.toUpper)\n \n const magicFn = products => customers => {\n const getCustomerProducts = filterProducts(products)\n \n return R.reduce((acc, customer) => ({\n ...acc,\n [getUpperName(customer)]: R.map(getName, getCustomerProducts(customer))\n }), {}, customers)\n }\n \n return magicFn(products)(customers)\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":484,"value":"md`\n## Data & Libraries\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":215,"value":"products = [{\n id: 1,\n name: 'Shirt - M (S)',\n sex: 'M',\n size: 'S',\n type: 'shirt'\n}, {\n id: 2,\n name: 'Shirt - M (M)',\n sex: 'M',\n size: 'M',\n type: 'shirt'\n}, {\n id: 3,\n name: 'Shirt - M (L)',\n sex: 'M',\n size: 'L',\n type: 'shirt'\n}, {\n id: 4,\n name: 'Shirt - F (S)',\n sex: 'F',\n size: 'S',\n type: 'shirt'\n}, {\n id: 5,\n name: 'Shirt - F (M)',\n sex: 'F',\n size: 'M',\n type: 'shirt'\n}, {\n id: 6,\n name: 'Shirt - F (L)',\n sex: 'F',\n size: 'L',\n type: 'shirt'\n}, {\n id: 7,\n name: 'Pants - M (S)',\n sex: 'M',\n size: 'S',\n type: 'pants'\n}, {\n id: 8,\n name: 'Pants - M (M)',\n sex: 'M',\n size: 'M',\n type: 'pants'\n}, {\n id: 9,\n name: 'Pants - M (L)',\n sex: 'M',\n size: 'L',\n type: 'pants'\n}, {\n id: 10,\n name: 'Pants - F (S)',\n sex: 'F',\n size: 'S',\n type: 'pants'\n}, {\n id: 11,\n name: 'Pants - F (M)',\n sex: 'F',\n size: 'M',\n type: 'pants'\n}, {\n id: 12,\n name: 'Pants - F (L)',\n sex: 'F',\n size: 'L',\n type: 'pants'\n}]","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":304,"value":"customers = [{\n id: 1,\n name: 'John Doe',\n sex: 'M',\n size: 'M'\n}, {\n id: 2,\n name: 'Samantha Smith',\n sex: 'F',\n size: 'S'\n}, {\n id: 3,\n name: 'Foolbert Bartinsky',\n sex: 'M',\n size: 'M'\n}, {\n id: 4,\n name: 'Bazilura Quxtor',\n sex: 'F',\n size: 'M'\n}, {\n id: 5,\n name: 'Loremius Ipsor',\n sex: 'M',\n size: 'L'\n}]","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":488,"value":"R = import('https://unpkg.com/ramda@0.25.0/es/index.js?module')","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":491,"value":"Reselect = import('reselect')","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W45","stdlib":"1"}} 44:"$43:body"