## String

#### byteSize

Returns the length of a string in bytes.

Convert a given string to a `Blob` Object and find its `size`.

    const byteSize = str => new Blob([str]).size;

examples

    byteSize('😀'); // 4
    byteSize('Hello World'); // 11

#### capitalize

Capitalizes the first letter of a string.

Use array destructuring and `String.toUpperCase()` to capitalize first letter, `...rest` to get array of characters after first letter and then `Array.join('')` to make it a string again. Omit the `lowerRest` parameter to keep the rest of the string intact, or set it to `true` to convert to lowercase.

    const capitalize = ([first, ...rest], lowerRest = false) =>
      first.toUpperCase() + (lowerRest ? rest.join('').toLowerCase() : rest.join(''));

examples

    capitalize('fooBar'); // 'FooBar'
    capitalize('fooBar', true); // 'Foobar'

#### capitalizeEveryWord

Capitalizes the first letter of every word in a string.

Use `String.replace()` to match the first character of each word and `String.toUpperCase()` to capitalize it.

    const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperCase());

examples

    capitalizeEveryWord('hello world!'); // 'Hello World!'

#### CSVToArray

Converts a comma-separated values (CSV) string to a 2D array.

Use `Array.slice()` and `Array.indexOf('\n')` to remove the first row (title row) if `omitFirstRow` is `true`. Use `String.split('\n')` to create a string for each row, then `String.split(delimiter)` to separate the values in each row. Omit the second argument, `delimiter`, to use a default delimiter of `,`. Omit the third argument, `omitFirstRow`, to include the first row (title row) of the CSV string.

    const CSVToArray = (data, delimiter = ',', omitFirstRow = false) =>
      data
        .slice(omitFirstRow ? data.indexOf('\n') + 1 : 0)
        .split('\n')
        .map(v => v.split(delimiter));

examples

    CSVToArray('a,b\nc,d'); // [['a','b'],['c','d']];
    CSVToArray('a;b\nc;d', ';'); // [['a','b'],['c','d']];
    CSVToArray('col1,col2\na,b\nc,d', ',', true); // [['a','b'],['c','d']];

#### CSVToJSON

Converts a comma-separated values (CSV) string to a 2D array of objects. The first row of the string is used as the title row.

Use `Array.slice()` and `Array.indexOf('\n')` and `String.split(delimiter)` to separate the first row (title row) into values. Use `String.split('\n')` to create a string for each row, then `Array.map()` and `String.split(delimiter)` to separate the values in each row. Use `Array.reduce()` to create an object for each row's values, with the keys parsed from the title row. Omit the second argument, `delimiter`, to use a default delimiter of `,`.

    const CSVToJSON = (data, delimiter = ',') => {
      const titles = data.slice(0, data.indexOf('\n')).split(delimiter);
      return data
        .slice(data.indexOf('\n') + 1)
        .split('\n')
        .map(v => {
          const values = v.split(delimiter);
          return titles.reduce((obj, title, index) => ((obj[title] = values[index]), obj), {});
        });
    };

examples

    CSVToJSON('col1,col2\na,b\nc,d'); // [{'col1': 'a', 'col2': 'b'}, {'col1': 'c', 'col2': 'd'}];
    CSVToJSON('col1;col2\na;b\nc;d', ';'); // [{'col1': 'a', 'col2': 'b'}, {'col1': 'c', 'col2': 'd'}];

#### decapitalize

Decapitalizes the first letter of a string.

Use array destructuring and `String.toLowerCase()` to decapitalize first letter, `...rest` to get array of characters after first letter and then `Array.join('')` to make it a string again. Omit the `upperRest` parameter to keep the rest of the string intact, or set it to `true` to convert to uppercase.

    const decapitalize = ([first, ...rest], upperRest = false) =>
      first.toLowerCase() + (upperRest ? rest.join('').toUpperCase() : rest.join(''));

examples

    decapitalize('FooBar'); // 'fooBar'
    decapitalize('FooBar', true); // 'fOOBAR'

#### escapeHTML

Escapes a string for use in HTML.

Use `String.replace()` with a regexp that matches the characters that need to be escaped, using a callback function to replace each character instance with its associated escaped character using a dictionary (object).

    const escapeHTML = str =>
      str.replace(
        /[&<>'"]/g,
        tag =>
          ({
            '&': '&amp;',
            '<': '&lt;',
            '>': '&gt;',
            "'": '&#39;',
            '"': '&quot;'
          }[tag] || tag)
      );

examples

    escapeHTML('<a href="#">Me & you</a>'); // '&lt;a href=&quot;#&quot;&gt;Me &amp; you&lt;/a&gt;'

#### escapeRegExp

Escapes a string to use in a regular expression.

Use `String.replace()` to escape special characters.

    const escapeRegExp = str => str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');

examples

    escapeRegExp('(test)'); // \\(test\\)

#### fromCamelCase

Converts a string from camelcase.

Use `String.replace()` to remove underscores, hyphens, and spaces and convert words to camelcase. Omit the second argument to use a default `separator` of `_`.

    const fromCamelCase = (str, separator = '_') =>
      str
        .replace(/([a-z\d])([A-Z])/g, '$1' + separator + '$2')
        .replace(/([A-Z]+)([A-Z][a-z\d]+)/g, '$1' + separator + '$2')
        .toLowerCase();

examples

    fromCamelCase('someDatabaseFieldName', ' '); // 'some database field name'
    fromCamelCase('someLabelThatNeedsToBeCamelized', '-'); // 'some-label-that-needs-to-be-camelized'
    fromCamelCase('someJavascriptProperty', '_'); // 'some_javascript_property'

#### indentString

Indents each line in the provided string.

Use `String.replace` and a regular expression to add the character specified by `indent` `count` times at the start of each line. Omit the third parameter, `indent`, to use a default indentation character of `' '`.

    const indentString = (str, count, indent = ' ') => str.replace(/^/gm, indent.repeat(count));

examples

    indentString('Lorem\nIpsum', 2); // '  Lorem\n  Ipsum'
    indentString('Lorem\nIpsum', 2, '_'); // '__Lorem\n__Ipsum'

#### isAbsoluteURL

Returns `true` if the given string is an absolute URL, `false` otherwise.

Use a regular expression to test if the string is an absolute URL.

    const isAbsoluteURL = str => /^[a-z][a-z0-9+.-]*:/.test(str);

examples

    isAbsoluteURL('https://google.com'); // true
    isAbsoluteURL('ftp://www.myserver.net'); // true
    isAbsoluteURL('/foo/bar'); // false

#### isAnagram

Checks if a string is an anagram of another string (case-insensitive, ignores spaces, punctuation and special characters).

Use `String.toLowerCase()`, `String.replace()` with an appropriate regular expression to remove unnecessary characters, `String.split('')`, `Array.sort()` and `Array.join('')` on both strings to normalize them, then check if their normalized forms are equal.

    const isAnagram = (str1, str2) => {
      const normalize = str =>
        str
          .toLowerCase()
          .replace(/[^a-z0-9]/gi, '')
          .split('')
          .sort()
          .join('');
      return normalize(str1) === normalize(str2);
    };

examples

    isAnagram('iceman', 'cinema'); // true

#### isLowerCase

Checks if a string is lower case.

Convert the given string to lower case, using `String.toLowerCase()` and compare it to the original.

    const isLowerCase = str => str === str.toLowerCase();

examples

    isLowerCase('abc'); // true
    isLowerCase('a3@$'); // true
    isLowerCase('Ab4'); // false

#### isUpperCase

Checks if a string is upper case.

Convert the given string to upper case, using `String.toUpperCase()` and compare it to the original.

    const isUpperCase = str => str === str.toUpperCase();

examples

    isUpperCase('ABC'); // true
    isLowerCase('A3@$'); // true
    isLowerCase('aB4'); // false

#### mapString

Creates a new string with the results of calling a provided function on every character in the calling string.

Use `String.split('')` and `Array.map()` to call the provided function, `fn`, for each character in `str`. Use `Array.join('')` to recombine the array of characters into a string. The callback function, `fn`, takes three arguments (the current character, the index of the current character and the string `mapString` was called upon).

    const mapString = (str, fn) =>
      str
        .split('')
        .map((c, i) => fn(c, i, str))
        .join('');

examples

    mapString('lorem ipsum', c => c.toUpperCase()); // 'LOREM IPSUM'

#### mask

Replaces all but the last `num` of characters with the specified mask character.

Use `String.slice()` to grab the portion of the characters that will remain unmasked and use `String.padStart()` to fill the beginning of the string with the mask character up to the original length. Omit the second argument, `num`, to keep a default of `4` characters unmasked. If `num` is negative, the unmasked characters will be at the start of the string. Omit the third argument, `mask`, to use a default character of `'*'` for the mask.

    const mask = (cc, num = 4, mask = '*') => `${cc}`.slice(-num).padStart(`${cc}`.length, mask);

examples

    mask(1234567890); // '******7890'
    mask(1234567890, 3); // '*******890'
    mask(1234567890, -4, '$'); // '$$$$567890'

#### pad

Pads a string on both sides with the specified character, if it's shorter than the specified length.

Use `String.padStart()` and `String.padEnd()` to pad both sides of the given string. Omit the third argument, `char`, to use the whitespace character as the default padding character.

    const pad = (str, length, char = ' ') =>
      str.padStart((str.length + length) / 2, char).padEnd(length, char);

examples

    pad('cat', 8); // '  cat   '
    pad(String(42), 6, '0'); // '004200'
    pad('foobar', 3); // 'foobar'

#### palindrome

Returns `true` if the given string is a palindrome, `false` otherwise.

Convert string `String.toLowerCase()` and use `String.replace()` to remove non-alphanumeric characters from it. Then, use the spread operator (`...`) to split string into individual characters, `Array.reverse()`, `String.join('')` and compare to the original, unreversed string, after converting it `String.tolowerCase()`.

    const palindrome = str => {
      const s = str.toLowerCase().replace(/[\W_]/g, '');
      return s === [...s].reverse().join('');
    };

examples

    palindrome('taco cat'); // true

#### pluralize

Returns the singular or plural form of the word based on the input number. If the first argument is an `object`, it will use a closure by returning a function that can auto-pluralize words that don't simply end in `s` if the supplied dictionary contains the word.

If `num` is either `-1` or `1`, return the singular form of the word. If `num` is any other number, return the plural form. Omit the third argument to use the default of the singular word + `s`, or supply a custom pluralized word when necessary. If the first argument is an `object`, utilize a closure by returning a function which can use the supplied dictionary to resolve the correct plural form of the word.

    const pluralize = (val, word, plural = word + 's') => {
      const _pluralize = (num, word, plural = word + 's') =>
        [1, -1].includes(Number(num)) ? word : plural;
      if (typeof val === 'object') return (num, word) => _pluralize(num, word, val[word]);
      return _pluralize(val, word, plural);
    };

examples

    pluralize(0, 'apple'); // 'apples'
    pluralize(1, 'apple'); // 'apple'
    pluralize(2, 'apple'); // 'apples'
    pluralize(2, 'person', 'people'); // 'people'

    const PLURALS = {
      person: 'people',
      radius: 'radii'
    };
    const autoPluralize = pluralize(PLURALS);
    autoPluralize(2, 'person'); // 'people'

#### removeNonASCII

Removes non-printable ASCII characters.

Use a regular expression to remove non-printable ASCII characters.

    const removeNonASCII = str => str.replace(/[^\x20-\x7E]/g, '');

examples

    removeNonASCII('äÄçÇéÉêlorem-ipsumöÖÐþúÚ'); // 'lorem-ipsum'

#### reverseString

Reverses a string.

Use the spread operator (`...`) and `Array.reverse()` to reverse the order of the characters in the string. Combine characters to get a string using `String.join('')`.

    const reverseString = str => [...str].reverse().join('');

examples

    reverseString('foobar'); // 'raboof'

#### sortCharactersInString

Alphabetically sorts the characters in a string.

Use the spread operator (`...`), `Array.sort()` and `String.localeCompare()` to sort the characters in `str`, recombine using `String.join('')`.

    const sortCharactersInString = str => [...str].sort((a, b) => a.localeCompare(b)).join('');

examples

    sortCharactersInString('cabbage'); // 'aabbceg'

#### splitLines

Splits a multiline string into an array of lines.

Use `String.split()` and a regular expression to match line breaks and create an array.

    const splitLines = str => str.split(/\r?\n/);

examples

    splitLines('This\nis a\nmultiline\nstring.\n'); // ['This', 'is a', 'multiline', 'string.' , '']

#### stringPermutations

⚠️ WARNING: This function's execution time increases exponentially with each character. Anything more than 8 to 10 characters will cause your browser to hang as it tries to solve all the different combinations.

Generates all permutations of a string (contains duplicates).

Use recursion. For each letter in the given string, create all the partial permutations for the rest of its letters. Use `Array.map()` to combine the letter with each partial permutation, then `Array.reduce()` to combine all permutations in one array. Base cases are for string `length` equal to `2` or `1`.

    const stringPermutations = str => {
      if (str.length <= 2) return str.length === 2 ? [str, str[1] + str[0]] : [str];
      return str
        .split('')
        .reduce(
          (acc, letter, i) =>
            acc.concat(stringPermutations(str.slice(0, i) + str.slice(i + 1)).map(val => letter + val)),
          []
        );
    };

examples

    stringPermutations('abc'); // ['abc','acb','bac','bca','cab','cba']

#### stripHTMLTags

Removes HTML/XML tags from string.

Use a regular expression to remove HTML/XML tags from a string.

    const stripHTMLTags = str => str.replace(/<[^>]*>/g, '');

examples

    stripHTMLTags('<p><em>lorem</em> <strong>ipsum</strong></p>'); // 'lorem ipsum'

#### toCamelCase

Converts a string to camelcase.

Break the string into words and combine them capitalizing the first letter of each word, using a regexp.

    const toCamelCase = str => {
      let s =
        str &&
        str
          .match(/[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g)
          .map(x => x.slice(0, 1).toUpperCase() + x.slice(1).toLowerCase())
          .join('');
      return s.slice(0, 1).toLowerCase() + s.slice(1);
    };

examples

    toCamelCase('some_database_field_name'); // 'someDatabaseFieldName'
    toCamelCase('Some label that needs to be camelized'); // 'someLabelThatNeedsToBeCamelized'
    toCamelCase('some-javascript-property'); // 'someJavascriptProperty'
    toCamelCase('some-mixed_string with spaces_underscores-and-hyphens'); // 'someMixedStringWithSpacesUnderscoresAndHyphens'

#### toKebabCase

Converts a string to kebab case.

Break the string into words and combine them adding `-` as a separator, using a regexp.

    const toKebabCase = str =>
      str &&
      str
        .match(/[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g)
        .map(x => x.toLowerCase())
        .join('-');

examples

    toKebabCase('camelCase'); // 'camel-case'
    toKebabCase('some text'); // 'some-text'
    toKebabCase('some-mixed_string With spaces_underscores-and-hyphens'); // 'some-mixed-string-with-spaces-underscores-and-hyphens'
    toKebabCase('AllThe-small Things'); // "all-the-small-things"
    toKebabCase('IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML'); // "i-am-listening-to-fm-while-loading-different-url-on-my-browser-and-also-editing-xml-and-html"

#### toSnakeCase

Converts a string to snake case.

Break the string into words and combine them adding `_` as a separator, using a regexp.

    const toSnakeCase = str =>
      str &&
      str
        .match(/[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g)
        .map(x => x.toLowerCase())
        .join('_');

examples

    toSnakeCase('camelCase'); // 'camel_case'
    toSnakeCase('some text'); // 'some_text'
    toSnakeCase('some-mixed_string With spaces_underscores-and-hyphens'); // 'some_mixed_string_with_spaces_underscores_and_hyphens'
    toSnakeCase('AllThe-small Things'); // "all_the_smal_things"
    toSnakeCase('IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML'); // "i_am_listening_to_fm_while_loading_different_url_on_my_browser_and_also_editing_some_xml_and_html"

#### truncateString

Truncates a string up to a specified length.

Determine if the string's `length` is greater than `num`. Return the string truncated to the desired length, with `'...'` appended to the end or the original string.

    const truncateString = (str, num) =>
      str.length > num ? str.slice(0, num > 3 ? num - 3 : num) + '...' : str;

examples

    truncateString('boomerang', 7); // 'boom...'

#### unescapeHTML

Unescapes escaped HTML characters.

Use `String.replace()` with a regex that matches the characters that need to be unescaped, using a callback function to replace each escaped character instance with its associated unescaped character using a dictionary (object).

    const unescapeHTML = str =>
      str.replace(
        /&amp;|&lt;|&gt;|&#39;|&quot;/g,
        tag =>
          ({
            '&amp;': '&',
            '&lt;': '<',
            '&gt;': '>',
            '&#39;': "'",
            '&quot;': '"'
          }[tag] || tag)
      );

examples

    unescapeHTML('&lt;a href=&quot;#&quot;&gt;Me &amp; you&lt;/a&gt;'); // '<a href="#">Me & you</a>'

#### URLJoin

Joins all given URL segments together, then normalizes the resulting URL.

Use `String.join('/')` to combine URL segments, then a series of `String.replace()` calls with various regexps to normalize the resulting URL (remove double slashes, add proper slashes for protocol, remove slashes before parameters, combine parameters with `'&'` and normalize first parameter delimiter).

    const URLJoin = (...args) =>
      args
        .join('/')
        .replace(/[\/]+/g, '/')
        .replace(/^(.+):\//, '$1://')
        .replace(/^file:/, 'file:/')
        .replace(/\/(\?|&|#[^!])/g, '$1')
        .replace(/\?/g, '&')
        .replace('&', '?');

examples

    URLJoin('http://www.google.com', 'a', '/b/cd', '?foo=123', '?bar=foo'); // 'http://www.google.com/a/b/cd?foo=123&bar=foo'

#### words

Converts a given string into an array of words.

Use `String.split()` with a supplied pattern (defaults to non-alpha as a regexp) to convert to an array of strings. Use `Array.filter()` to remove any empty strings. Omit the second argument to use the default regexp.

    const words = (str, pattern = /[^a-zA-Z-]+/) => str.split(pattern).filter(Boolean);

examples

    words('I love javaScript!!'); // ["I", "love", "javaScript"]
    words('python, javaScript & coffee'); // ["python", "javaScript", "coffee"]