function titleCase(str) {
  return str
    .toLowerCase()
    .split(" ")
    .map((w) => (w ? w[0].toUpperCase() + w.slice(1) : w))
    .join(" ");
}
titleCase("JAVASCRIPT is fun"); // "Javascript Is Fun"

Lowercasing first makes all-caps input work. Guard the empty w so repeated spaces don't throw.

sandbox.js

function titleCase(str) {
  // TODO
}

Output

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JavaScriptEasy8/15

Write titleCase(str) that uppercases the first letter of every word and lowercases the rest

By FrontendPro Editorial Team Updated 8/7/2026

Explore the JavaScript interview guide

Examples

Write titleCase so that the following cases hold.

InputtitleCase("hello world")
Output"Hello World"
InputtitleCase("JAVASCRIPT is fun")
Output"Javascript Is Fun"
InputtitleCase("a")
Output"A"

1 more hidden test cases - 4 in total will be graded.

Answer

function titleCase(str) {
  return str
    .toLowerCase()
    .split(" ")
    .map((w) => (w ? w[0].toUpperCase() + w.slice(1) : w))
    .join(" ");
}
titleCase("JAVASCRIPT is fun"); // "Javascript Is Fun"