freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/spinal-tap-case/index.md

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Spinal Tap Case

Spinal Tap Case

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Problem Explanation

Convert the given string to a lowercase sentence with words joined by dashes.

Relevant Links

• String global object
• JS Regex Resources
• JS String Prototype Replace
• JS String Prototype ToLowerCase

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Hints

Hint 1

Create a regular expression for all white spaces and underscores.

Hint 2

You will also have to make everything lowercase.

Hint 3

The tricky part is getting the regular expression part to work, once you do that then just turn the uppercase to lowercase and replace spaces with underscores using replace().

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Solutions

Solution 1 (Click to Show/Hide)

function spinalCase(str) {
  // Create a variable for the white space and underscores.
  var regex = /\s+|_+/g;

  // Replace low-upper case to low-space-uppercase
  str = str.replace(/([a-z])([A-Z])/g, "$1 $2");

  // Replace space and underscore with -
  return str.replace(regex, "-").toLowerCase();
}

// test here
spinalCase("This Is Spinal Tap");

Code Explanation

• regex contains the regular expression /\s+|_+/g, which will select all white spaces and underscores.
• The first replace() puts a space before any encountered uppercase characters in the string str so that the spaces can be replaced by dashes later on.
• While returning the string, another replace() replaces spaces and underscores with dashes using regex.

Solution 2 (Click to Show/Hide)

function spinalCase(str) {
  // Replace low-upper case to low-space-uppercase
  str = str.replace(/([a-z])([A-Z])/g, "$1 $2");
  // Split on whitespace and underscores and join with dash
  return str
    .toLowerCase()
    .split(/(?:_| )+/)
    .join("-");
}

// test here
spinalCase("This Is Spinal Tap");

Code Explanation

• Similar to the first solution, the first replace() puts a space before any encountered uppercase characters in the string str so that the spaces can be replaced by dashes later on.
• Instead of using replace() here to replace whitespace and underscores with dashes, the string is split() on the regular expression /(?:_| )+/ and join()-ed on -.

Relevant Links

• JS String Prototype Split
• JS Array Prototype Join

Solution 3 (Click to Show/Hide)

function spinalCase(str) {
  // "It's such a fine line between stupid, and clever."
  // --David St. Hubbins

  return str
    .split(/\s|_|(?=[A-Z])/)
    .join("-")
    .toLowerCase();
}

Code Explanation

• Split the string at one of the following conditions (converted to an array)
  • a whitespace character [\s] is encountered
  • underscore character [_] is encountered
  • or is followed by an uppercase letter [(?=[A-Z])]
• Join the array using a hyphen (-)
• Lowercase the whole resulting string

Relevant Links

• String#split
• RegExp
• Arrray#join
• String#toLowerCase