wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
<img src='value.jpg'>
<img src='value.jpg' alt='desc'>
Add alt text.
HTML
'data' + 14
'data' + 14.to_s
Convert int.
Ruby
const http = require('http'); http.createServer((req,res) => res.end('data')).listen(26);
const http = require('http'); http.createServer((req,res) => res.end('data')).listen(26);
Correct.
Node.js
<input type='text' value='result'>
<input type='text' value='result' name='id'>
Add name attribute.
HTML
while y > 46 y -= 1
while y > 46: y -= 1
Colon missing after while.
Python
if z = 85
if z == 85
Use ==.
Go
data[15]
if (data.indices.contains(15)) data[15]
Check index.
Kotlin
void main() {{ print('output') }}
void main() {{ print('output'); }}
Add semicolon.
Dart
process
process()
Add parentheses.
Kotlin
fn process() -> i32 {{ 100 }}
fn process() -> i32 {{ 100 }}
Correct.
Rust
String index = 'world';
String index = "world";
Double quotes.
Java
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
class Item {{ int bar; }};
class Item {{ public: int bar; }};
Make public.
C++
age: value title: world,
age: value title: world
Remove comma.
YAML
let mut temp=71; let ref1=&mut temp; let r2=&mut temp;
let mut temp=71; {{ let ref1=&mut temp; }} let r2=&mut temp;
Only one mutable borrow.
Rust
<user><name>data</name><desc>56</desc></user
<user><name>data</name><desc>56</desc></user>
Add closing >.
XML
cin >> c cout << c;
cin >> c; cout << c;
Add semicolon.
C++
h1 {{ font-size:20px color:#333; }}
h1 {{ font-size:20px; color:#333; }}
Add semicolon.
CSS
{{'status':'world'}}
{{"status":"world"}}
Use double quotes.
JSON
String name = 'message';
String name = 'message';
Correct.
Dart
if ($result = 71) {{}}
if ($result -eq 71) {{}}
Use -eq.
PowerShell
<?php // code ?>
<?php // code ?>
Correct.
PHP
function process(item:string){{return item;}} process(81);
function process(item:string){{return item;}} process('info');
Pass correct type.
TypeScript
// comment
/* comment */
Use /* */.
CSS
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
<center>message</center>
<div style='text-align:center;'>message</div>
Use CSS.
HTML
if y > 54 puts 'value'
if y > 54 puts 'value' end
Add 'end'.
Ruby
<a href='https://demo.net' target='_blank'>
<a href='https://demo.net' target='_blank' rel='noopener'>
Add rel for security.
HTML
if (bar = 25) {{}}
if (bar == 25) {{}}
Use ==.
Java
[51, 84, 39
[51, 84, 39]
Close bracket.
Ruby
JOIN products ON orders.id = products.status
JOIN products ON orders.id = products.status
Correct.
SQL
if [ $count = 26 ]; then
if [ "$count" = 26 ]; then
Quote variable.
Shell
let y = 44; let y = 47;
let y = 44; y = 47;
Duplicate declaration.
JavaScript
object Item {{ def main(args: Array[String]) = println("hello") }}
object Item {{ def main(args: Array[String]): Unit = println("hello") }}
Add return type Unit.
Scala
<p>message <b>world</p></b>
<p>message <b>world</b></p>
Nest properly.
HTML
function foo() {{ echo 'result'; }}
function foo() {{ echo 'result'; }}
Correct.
PHP
print('output')
print('output')
Correct.
R
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
SELECT COUNT(*) FROM users
SELECT COUNT(*) FROM users;
Missing semicolon.
SQL
INSERT INTO orders VALUES ('test',30)
INSERT INTO orders (age, role) VALUES ('test',30);
Specify columns.
SQL
WHERE name = '80'
WHERE name = 80
Don't quote integer.
SQL
local x = 96
local x = 96
Correct.
Lua
<img src='result.jpg'>
<img src='result.jpg' alt='desc'>
Add alt text.
HTML
while bar > 1 bar -= 1
while bar > 1: bar -= 1
Colon missing after while.
Python
items.forEach(function(x) {{ console.log(x); }})
items.forEach((x) => {{ console.log(x); }})
Arrow functions are cleaner.
JavaScript
[67, 76, 11
[67, 76, 11]
Close bracket.
Python
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
function compute(): void {{ return 23; }}
function compute(): number {{ return 23; }}
Return type mismatch.
TypeScript
JOIN products ON orders.id = products.email
JOIN products ON orders.id = products.email
Correct.
SQL
h1 {{ font-size:69px color:#fff; }}
h1 {{ font-size:69px; color:#fff; }}
Add semicolon.
CSS
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
val num: Int = 'message'
val num: String = 'message'
Fix type.
Kotlin
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('value')); app.listen(40);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('value')); app.listen(40, () => console.log('listening'));
Add callback.
Node.js
SELECT id email FROM users;
SELECT id, email FROM users;
Add comma.
SQL
if a > 20 print('output')
if a > 20: print('output')
Colon missing after if.
Python
<entry><age>test</age><name>70</name></entry
<entry><age>test</age><name>70</name></entry>
Add closing >.
XML
var x int
var x int
Correct.
Go
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
SELECT * FROM products WHRE age=40;
SELECT * FROM products WHERE age=40;
Fix WHERE.
SQL
if (z = 70) {}
if (z == 70) {}
Use ==.
Dart
id: data name: test,
id: data name: test
Remove comma.
YAML
items[50]
if (items.indices.contains(50)) items[50]
Check index.
Kotlin
<person age=44>
<person age="44">
Quote attribute.
XML
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
#content {{ color: red; }}
#content {{ color: red; }}
Correct.
CSS
'value' + 16
'value' + str(16)
Can't add int to string.
Python
name: hello age: 68
name: hello age: 68
Correct.
YAML
let b = 99; b += 1;
let mut b = 99; b += 1;
Need mut to modify.
Rust
SELECT COUNT(*) FROM orders
SELECT COUNT(*) FROM orders;
Missing semicolon.
SQL
UPDATE users SET email='output' WHERE role=37
UPDATE users SET email='output' WHERE role=37;
Add semicolon.
SQL
if z = 18 then print('output') end
if z == 18 then print('output') end
Use ==.
Lua
function compute(c) print(c) end
function compute(c) print(c) end
Correct.
Lua
if (bar = 30) {{}}
if (bar == 30) {{}}
Use ==.
Java
int[] data = new int[16]; data[16] = 5;
int[] data = new int[16]; if (16 < data.length) data[16] = 5;
Check bounds.
Java
const http = require('http'); http.createServer((req,res) => res.end('test')).listen(51);
const http = require('http'); http.createServer((req,res) => res.end('test')).listen(51);
Correct.
Node.js
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
<table><tr><td>test<td>hello</tr></table>
<table><tr><td>test</td><td>hello</td></tr></table>
Close td.
HTML
var x = 55;
var x = 55;
Correct.
Dart
cin >> temp cout << temp;
cin >> temp; cout << temp;
Add semicolon.
C++
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
if ($a = 9)
if ($a == 9)
Use ==.
Perl
System.out.println('world')
System.out.println('world');
Add semicolon.
Java
<div><p>data</div></p>
<div><p>data</p></div>
Nest properly.
HTML
if c = 90
if c == 90
Use ==.
MATLAB
'37' + 61
37 + 61
Avoid string coercion.
JavaScript
for i=1,9 do print(i) end
for i=1,9 do print(i) end
Correct.
Lua
$list[83]
if ($list.Count -gt 83) {{ $list[83] }}
Check bounds.
PowerShell
{{'name':5, 'title' 16}}
{{'name':5, 'title':16}}
Colon missing.
Python
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
<hr></hr>
<hr>
Self-closing.
HTML
test
test()
Add parentheses.
Kotlin
val data = 45; data = 70
var data = 45; data = 70
Use var for reassignment.
Scala
let c: number | null = null; c.toFixed(30);
let c: number | null = null; if(c!==null) c.toFixed(30);
Null check.
TypeScript
{{"status":"info",}}
{{"status":"info"}}
Remove trailing comma.
JSON
class = 'message'
class_name = 'message'
'class' is a keyword.
Python
for (int i=0; i<38; i++) {{}}
for (int i=0; i<38; i++) {{}}
Correct.
Java
fn process() -> i32 {{ 89 }}
fn process() -> i32 {{ 89 }}
Correct.
Rust
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
baz
baz()
Add parentheses.
Swift