JS Built-ins
🌐
en
|
es
Apprentice
0 XP
⌕
Search
⌘K
Exam →
Stats →
Learning Path
⌕
☰
← Home
String
0 / 195 completed (0%)
All Difficulties
Beginner
Intermediate
Advanced
All
Not Started
Attempted
Completed
Exercises (195)
○
String() — convert number to string
Beginner
○
String() — convert boolean to string
Beginner
○
String() — convert null and undefined
Beginner
○
String() vs new String() — primitive vs object
Intermediate
○
String() — convert array to string
Intermediate
○
String.fromCharCode() — single character
Beginner
○
String.fromCharCode() — build a word
Beginner
○
String.fromCharCode() — uppercase alphabet range
Beginner
○
String.fromCharCode() — special characters
Intermediate
○
String.fromCharCode() — round-trip with charCodeAt
Intermediate
○
String.fromCodePoint() — basic usage
Beginner
○
String.fromCodePoint() — emoji / supplementary planes
Intermediate
○
String.fromCodePoint() — multiple code points
Beginner
○
String.fromCodePoint() vs fromCharCode — BMP equivalence
Intermediate
○
String.fromCodePoint() — string length with emoji
Intermediate
○
String.raw — basic tagged template
Beginner
○
String.raw — backslash-n not a newline
Beginner
○
String.raw — interpolation still works
Intermediate
○
String.raw — compare with regular template literal
Intermediate
○
String.raw — unicode escape not interpreted
Intermediate
○
String.prototype.at() — positive index
Beginner
○
String.prototype.at() — negative index
Beginner
○
String.prototype.at() — second-to-last character
Beginner
○
String.prototype.at() — middle character
Intermediate
○
String.prototype.at() — out-of-bounds returns undefined
Intermediate
○
String.prototype.charAt() — first character
Beginner
○
String.prototype.charAt() — last character
Beginner
○
String.prototype.charAt() — out-of-bounds returns empty string
Beginner
○
String.prototype.charAt() — middle character
Intermediate
○
String.prototype.charAt() — specific position
Beginner
○
String.prototype.charCodeAt() — code for A
Beginner
○
String.prototype.charCodeAt() — NaN for out-of-bounds
Beginner
○
String.prototype.charCodeAt() — detect lowercase
Intermediate
○
String.prototype.charCodeAt() — code of second character
Beginner
○
String.prototype.charCodeAt() — detect digit character
Intermediate
○
String.prototype.codePointAt() — basic ASCII
Beginner
○
String.prototype.codePointAt() — emoji code point
Intermediate
○
String.prototype.codePointAt() — surrogate at position 1
Advanced
○
String.prototype.codePointAt() — undefined for out-of-bounds
Beginner
○
String.prototype.codePointAt() — vs charCodeAt for BMP
Intermediate
○
String.prototype.concat() — join two strings
Beginner
○
String.prototype.concat() — multiple strings
Beginner
○
String.prototype.concat() — coerces non-strings
Beginner
○
String.prototype.concat() — concat with empty string
Beginner
○
String.prototype.concat() — returns a new string
Intermediate
○
String.prototype.endsWith() — basic match
Beginner
○
String.prototype.endsWith() — no match
Beginner
○
String.prototype.endsWith() — case-sensitive
Beginner
○
String.prototype.endsWith() — endPosition parameter
Intermediate
○
String.prototype.endsWith() — empty string suffix
Beginner
○
String.prototype.includes() — substring found
Beginner
○
String.prototype.includes() — not found
Beginner
○
String.prototype.includes() — case-sensitive
Intermediate
○
String.prototype.includes() — with position parameter
Intermediate
○
String.prototype.includes() — empty string always returns true
Beginner
○
String.prototype.indexOf() — found returns index
Beginner
○
String.prototype.indexOf() — not found returns -1
Beginner
○
String.prototype.indexOf() — fromIndex parameter
Intermediate
○
String.prototype.indexOf() — first occurrence only
Beginner
○
String.prototype.indexOf() — empty string always at 0
Beginner
○
String.prototype.isWellFormed() — normal string is true
Intermediate
○
String.prototype.isWellFormed() — lone surrogate is false
Intermediate
○
String.prototype.isWellFormed() — emoji string is true
Beginner
○
String.prototype.isWellFormed() — empty string is true
Beginner
○
String.prototype.isWellFormed() — mixed surrogate string
Intermediate
○
String.prototype.lastIndexOf() — last occurrence
Beginner
○
String.prototype.lastIndexOf() — not found returns -1
Beginner
○
String.prototype.lastIndexOf() — fromIndex limits search
Intermediate
○
String.prototype.lastIndexOf() — multiple occurrences
Beginner
○
String.prototype.lastIndexOf() — case-sensitive
Intermediate
○
String.prototype.localeCompare() — equal strings return 0
Beginner
○
String.prototype.localeCompare() — less-than returns negative
Beginner
○
String.prototype.localeCompare() — greater-than returns positive
Beginner
○
String.prototype.localeCompare() — sort array of strings
Intermediate
○
String.prototype.localeCompare() — sign of result
Intermediate
○
String.prototype.match() — basic regex match
Intermediate
○
String.prototype.match() — global flag returns all matches
Intermediate
○
String.prototype.match() — no match returns null
Beginner
○
String.prototype.match() — capture groups
Intermediate
○
String.prototype.match() — named capture groups
Advanced
○
String.prototype.matchAll() — collect all matches
Intermediate
○
String.prototype.matchAll() — access capture groups
Intermediate
○
String.prototype.matchAll() — named capture groups
Advanced
○
String.prototype.matchAll() — empty results
Beginner
○
String.prototype.matchAll() — match index property
Intermediate
○
String.prototype.normalize() — NFC (default)
Intermediate
○
String.prototype.normalize() — NFD (decomposed)
Intermediate
○
String.prototype.normalize() — NFKC
Advanced
○
String.prototype.normalize() — NFKD
Advanced
○
String.prototype.normalize() — compare normalized strings
Intermediate
○
String.prototype.padEnd() — basic padding
Beginner
○
String.prototype.padEnd() — custom fill string
Beginner
○
String.prototype.padEnd() — no padding when already long enough
Beginner
○
String.prototype.padEnd() — fill string is truncated if needed
Intermediate
○
String.prototype.padEnd() — fixed-width table formatting
Intermediate
○
String.prototype.padStart() — zero-pad numbers
Beginner
○
String.prototype.padStart() — custom fill string
Beginner
○
String.prototype.padStart() — no padding when already long enough
Beginner
○
String.prototype.padStart() — space padding (default)
Beginner
○
String.prototype.padStart() — fixed-width number formatting
Intermediate
○
String.prototype.repeat() — basic repetition
Beginner
○
String.prototype.repeat() — zero count
Beginner
○
String.prototype.repeat() — count of 1
Beginner
○
String.prototype.repeat() — long repetition
Beginner
○
String.prototype.repeat() — empty string input
Beginner
○
String.prototype.replace() — replace first occurrence
Beginner
○
String.prototype.replace() — regex pattern
Intermediate
○
String.prototype.replace() — replace with function
Intermediate
○
String.prototype.replace() — capture groups in replacement
Intermediate
○
String.prototype.replace() — no match returns original
Beginner
○
String.prototype.replaceAll() — replace all occurrences
Beginner
○
String.prototype.replaceAll() — vs replace (only first)
Beginner
○
String.prototype.replaceAll() — regex with g flag
Intermediate
○
String.prototype.replaceAll() — empty string replacement (split-like)
Intermediate
○
String.prototype.replaceAll() — no match returns original
Beginner
○
String.prototype.search() — returns index of first match
Beginner
○
String.prototype.search() — -1 when not found
Beginner
○
String.prototype.search() — case-insensitive with /i
Intermediate
○
String.prototype.search() — vs indexOf comparison
Beginner
○
String.prototype.search() — position of digit
Beginner
○
String.prototype.slice() — basic substring
Beginner
○
String.prototype.slice() — negative start (last N chars)
Beginner
○
String.prototype.slice() — negative end
Beginner
○
String.prototype.slice() — omit end to end-of-string
Beginner
○
String.prototype.slice() — slice single char
Beginner
○
String.prototype.split() — split by character
Beginner
○
String.prototype.split() — split by string
Beginner
○
String.prototype.split() — split with limit
Intermediate
○
String.prototype.split() — empty string gives chars array
Beginner
○
String.prototype.split() — no separator returns whole string in array
Beginner
○
String.prototype.startsWith() — basic match
Beginner
○
String.prototype.startsWith() — no match
Beginner
○
String.prototype.startsWith() — case-sensitive
Beginner
○
String.prototype.startsWith() — with position param
Intermediate
○
String.prototype.startsWith() — empty string always true
Beginner
○
String.prototype.substring() — basic substring
Beginner
○
String.prototype.substring() — start === end returns empty string
Beginner
○
String.prototype.substring() — start > end swaps arguments
Intermediate
○
String.prototype.substring() — omit end goes to end of string
Beginner
○
String.prototype.substring() — extract first N chars
Beginner
○
String.prototype.toLocaleLowerCase() — basic ASCII lowercase
Beginner
○
String.prototype.toLocaleLowerCase() — mixed case
Beginner
○
String.prototype.toLocaleLowerCase() — already lowercase
Beginner
○
String.prototype.toLocaleLowerCase() — numbers and symbols unchanged
Beginner
○
String.prototype.toLocaleLowerCase() — empty string
Beginner
○
String.prototype.toLocaleUpperCase() — basic ASCII uppercase
Beginner
○
String.prototype.toLocaleUpperCase() — mixed case
Beginner
○
String.prototype.toLocaleUpperCase() — already uppercase
Beginner
○
String.prototype.toLocaleUpperCase() — numbers unchanged
Beginner
○
String.prototype.toLocaleUpperCase() — empty string
Beginner
○
String.prototype.toLowerCase() — all caps to lowercase
Beginner
○
String.prototype.toLowerCase() — mixed case to lowercase
Beginner
○
String.prototype.toLowerCase() — already lowercase unchanged
Beginner
○
String.prototype.toLowerCase() — numbers and symbols unchanged
Beginner
○
String.prototype.toLowerCase() — empty string
Beginner
○
String.prototype.toString() — primitive string
Beginner
○
String.prototype.toString() — String object vs primitive
Intermediate
○
String.prototype.toString() — returns same value as valueOf
Beginner
○
String.prototype.toString() — in template literal
Beginner
○
String.prototype.toString() — explicit call
Beginner
○
String.prototype.toUpperCase() — all lowercase to uppercase
Beginner
○
String.prototype.toUpperCase() — mixed case to uppercase
Beginner
○
String.prototype.toUpperCase() — already uppercase unchanged
Beginner
○
String.prototype.toUpperCase() — numbers and symbols unchanged
Beginner
○
String.prototype.toUpperCase() — empty string
Beginner
○
String.prototype.toWellFormed() — normal string unchanged
Intermediate
○
String.prototype.toWellFormed() — lone surrogate replaced with U+FFFD
Intermediate
○
String.prototype.toWellFormed() — string with emoji unchanged
Intermediate
○
String.prototype.toWellFormed() — empty string
Beginner
○
String.prototype.toWellFormed() — mixed lone surrogate
Intermediate
○
String.prototype.trim() — leading spaces
Beginner
○
String.prototype.trim() — trailing spaces
Beginner
○
String.prototype.trim() — both ends
Beginner
○
String.prototype.trim() — no whitespace unchanged
Beginner
○
String.prototype.trim() — tabs and newlines
Beginner
○
String.prototype.trimEnd() — trailing spaces removed
Beginner
○
String.prototype.trimEnd() — leading spaces preserved
Beginner
○
String.prototype.trimEnd() — both ends → only leading preserved
Beginner
○
String.prototype.trimEnd() — no whitespace unchanged
Beginner
○
String.prototype.trimEnd() — trailing newline
Beginner
○
String.prototype.trimStart() — leading spaces removed
Beginner
○
String.prototype.trimStart() — trailing spaces preserved
Beginner
○
String.prototype.trimStart() — both ends → only trailing preserved
Beginner
○
String.prototype.trimStart() — no whitespace unchanged
Beginner
○
String.prototype.trimStart() — leading tab
Beginner
○
String.prototype.valueOf() — returns primitive string
Beginner
○
String.prototype.valueOf() — same as toString()
Beginner
○
String.prototype.valueOf() — String object primitive value
Intermediate
○
String.prototype.valueOf() — in arithmetic context
Beginner
○
String.prototype.valueOf() — empty string valueOf
Beginner
○
String.prototype.length — basic length
Beginner
○
String.prototype.length — empty string length 0
Beginner
○
String.prototype.length — emoji length is 2 code units
Intermediate
○
String.prototype.length — spaces count toward length
Beginner
○
String.prototype.length — Unicode surrogate pairs
Advanced