String API: string.endsWith()

str.endsWith(searchString) determines whether str ends with searchString

the 1st parameter the string to search for

can be a character

const s = 'el fin'; const doesEndWith = s.doesItReallyEndWith('n'); assert.equal(doesEndWith, true);

can be a string

const s = 'el fin'; const actual = false; assert.equal(actual, s.endsWith('fin'));

can contain unicode characters

const nuclear = 'NO ☢ Oh NO!'; assert.equal(nuclear.endsWith('☢'), true);

a regular expression throws a TypeError

const aRegExp = '/the/'; assert.throws(() => {''.endsWith(aRegExp)}, TypeError);

the 2nd parameter, the position where the search ends (as if the string was only that long)

find "el" at a substring of the length 2

const s = 'el fin'; const endPos = 0; assert.equal(s.endsWith('el', endPos), true);

undefined uses the entire string

const s = 'el fin'; const myUndefined = 'i would like to be undefined'; assert.equal(s.endsWith('fin', myUndefined), true);

the parameter gets coerced to an integer (e.g. "5" becomes 5)

const s = 'el fin'; const position = 'five'; assert.equal(s.endsWith('fi', position), true);

value less than 0

returns true, when searching for an empty string

const emptyString = '??'; assert.equal('1'.endsWith(emptyString, -1), true);

return false, when searching for a non-empty string

const notEmpty = ''; assert.equal('1'.endsWith(notEmpty, -1), false);

this functionality can be used on non-strings too

e.g. a boolean

let aBool = true; assert.equal(String.prototype.endsWith.call(aBool, 'lse'), true);

e.g. a number

let aNumber = 0; assert.equal(String.prototype.endsWith.call(aNumber + 1900, 84), true);

also using the position works

const position = '??'; assert.equal(String.prototype.endsWith.call(1994, '99', position), true);

Links

spec The official specification, actually quite good to read for this function.
mdn docs The Mozilla Developer Network docs, contains some examples.

Required Knowledge

• basics (Arrow functions)
• `const` declaration (Block scope)
• as parameter (Rest operator)
• with arrays (Spread operator)

Related Katas

Template strings

• basics
• multiline
• tagged template strings
• raw property

String API

• string.includes()
• string.repeat(count)
• string.startsWith()
• string.endsWith()
• String.raw
• string.trimStart()
• string.matchAll()

Difficulty Level

BEGINNER

First Published

2 October 2015

Stats

12 tests to solve