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JavaScript: Capitalize the first letter of a string

JavaScript fundamental (ES6 Syntax): Exercise-263 with Solution

Write a JavaScript program to capitalize the first letter of a string.

  • Use array destructuring and String.prototype.toUpperCase() to capitalize the first letter of the string.
  • Use Array.prototype.join('') to combine the capitalized first with the ...rest of the characters.
  • Omit the lowerRest argument to keep the rest of the string intact, or set it to true to convert to lowercase.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const capitalize = ([first, ...rest], lowerRest = false) =>
  first.toUpperCase() + (lowerRest ? rest.join('').toLowerCase() : rest.join(''));

console.log(capitalize('fooBar')); 
console.log(capitalize('fooBar', true));

Sample Output:

FooBar
Foobar

Pictorial Presentation:

JavaScript Fundamental: Capitalize the first letter of a string.

Flowchart:

flowchart: Capitalize the first letter of a string.

Live Demo:

See the Pen javascript-basic-exercise-263-1 by w3resource (@w3resource) on CodePen.


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Previous: Write a JavaScript program to create a base-64 encoded ASCII string from a String object in which each character in the string is treated as a byte of binary data.
Next: Write a JavaScript program to capitalize the first letter of every word in a string.

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JavaScript: Tips of the Day

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

const string = "foo";
const substring = "oo";

console.log(string.includes(substring));

includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found: 

var string = "foo";
var substring = "oo";

console.log(string.indexOf(substring) !== -1);

Ref: https://bit.ly/3fFFgZv