wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
<img src='message.jpg'>
<img src='message.jpg' alt='desc'>
Add alt text.
HTML
if ($a = 63) {{}}
if ($a -eq 63) {{}}
Use -eq.
PowerShell
var x = 43;
var x = 43;
Correct.
Dart
if index > 85 puts 'hello'
if index > 85 puts 'hello' end
Add 'end'.
Ruby
DELETE FROM products WHERE id=87
DELETE FROM products WHERE id=87;
Add semicolon.
SQL
my @arr = (45,82,52);
my @arr = (45,82,52);
Correct.
Perl
id: info age: data,
id: info age: data
Remove comma.
YAML
disp('hello')
disp('hello')
Correct.
MATLAB
const a = 16; a = 77;
let a = 16; a = 77;
Cannot reassign const.
JavaScript
let item = 'hello'
let item = "hello"
Double quotes.
Swift
String z = 'output';
String z = "output";
Double quotes.
Java
for (b in data)
for (b of data)
for...in iterates keys.
JavaScript
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
.Order {{ color: blue; }}
.Order {{ color: blue; }}
Correct.
CSS
class = 'info'
class_name = 'info'
'class' is a keyword.
Python
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
function process() {{ echo 'hello'; }}
function process() {{ echo 'hello'; }}
Correct.
PHP
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
{{"title":"test" "status":87}}
{{"title":"test", "status":87}}
Add comma.
JSON
if foo = 68
if foo == 68
Use ==.
Go
Product.save();
Product.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
def handle(): print('result')
def handle(): print('result')
Indent function body.
Python
33index = 10
index33 = 10
Variable cannot start with digit.
Python
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(92);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(92, () => console.log('listening'));
Add callback.
Node.js
sys.sqrt(9)
import sys sys.sqrt(9)
Import module first.
Python
fn process() -> i32 {{ 77 }}
fn process() -> i32 {{ 77 }}
Correct.
Rust
val b = 'data'
val b = "data"
Double quotes.
Kotlin
let a: Int = 'world'
let a: String = 'world'
Fix type.
Swift
if (y = 42)
if (y == 42)
Use ==.
Scala
{{"name":"world",}}
{{"name":"world"}}
Remove trailing comma.
JSON
print 'hello'
print('hello')
Parentheses for function call.
Lua
<hr></hr>
<hr>
Self-closing.
HTML
if (c = 27) {{}}
if (c == 27) {{}}
Use ==.
Java
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
UPDATE products SET age='result' WHERE role=51
UPDATE products SET age='result' WHERE role=51;
Add semicolon.
SQL
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
for (int i=0; i<26; i++) {{}}
for (int i=0; i<26; i++) {{}}
Correct.
Java
if ($c = 6)
if ($c == 6)
Use ==.
Perl
data.forEach(function(count) {{ console.log(count); }})
data.forEach((count) => {{ console.log(count); }})
Arrow functions are cleaner.
JavaScript
if foo = 67
if foo == 67
Use ==.
Ruby
class Person {{ int index; }};
class Person {{ public: int index; }};
Make public.
C++
h1 {{ font-size:50px color:#333; }}
h1 {{ font-size:50px; color:#333; }}
Add semicolon.
CSS
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
[x*x for x in values if x > 37]
[x*x for x in values if x > 37]
Correct list comprehension.
Python
const http = require('http'); http.createServer((req,res) => res.end('test')).listen(40);
const http = require('http'); http.createServer((req,res) => res.end('test')).listen(40);
Correct.
Node.js
def handle(index): return index + 1
def handle(index): return index + 1
Correct.
Python
yield result
yield result
Correct yield.
Python
fmt.Println 'hello'
fmt.Println('hello')
Missing parentheses.
Go
raise 'world'
raise Exception('world')
Raise needs an exception class.
Python
<note name='data'/>
<note name="data"/>
Double quotes.
XML
else print('world')
else: print('world')
Colon after else.
Python
System.out.println('result')
System.out.println('result');
Add semicolon.
Java
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
function foo(): void {{ return 26; }}
function foo(): number {{ return 26; }}
Return type mismatch.
TypeScript
assert temp > 10
assert temp > 10
Correct.
Python
JOIN profiles ON products.id = profiles.age
JOIN profiles ON products.id = profiles.age
Correct.
SQL
function render() {{ return {{key:'message'}} }}
function render() {{ return {{key:'message'}}; }}
Return object on same line.
JavaScript
$list[60]
if ($list.Count -gt 60) {{ $list[60] }}
Check bounds.
PowerShell
local a = 72
local a = 72
Correct.
Lua
const obj:Person = {{name:'test'}};
const obj:Person = {{name:'test', age:44}};
Add missing property.
TypeScript
// comment
/* comment */
Use /* */.
CSS
'23' + 17
23 + 17
Avoid string coercion.
JavaScript
<br></br>
<br>
Self-closing.
HTML
foo
foo()
Add parentheses.
Kotlin
[21, 58, 83
[21, 58, 83]
Close bracket.
Ruby
def render puts 'hello' end
def render puts 'hello' end
Correct.
Ruby
function process(c) print(c) end
function process(c) print(c) end
Correct.
Lua
if foo = 26 {{}}
if foo == 26 {{}}
Use ==.
Swift
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
<input type='text' value='test'>
<input type='text' value='test' name='age'>
Add name attribute.
HTML
let index: number | null = null; index.toFixed(70);
let index: number | null = null; if(index!==null) index.toFixed(70);
Null check.
TypeScript
while b > 3 b -= 1
while b > 3: b -= 1
Colon missing after while.
Python
if y = 18:
if y == 18:
Use == for comparison.
Python
if (item = 80) {{}}
if (item === 80) {{}}
Use === for equality.
JavaScript
if b > 96 print('result')
if b > 96: print('result')
Colon missing after if.
Python
{{'name':'data'}}
{{"name":"data"}}
Use double quotes.
JSON
SELECT COUNT(*) FROM users
SELECT COUNT(*) FROM users;
Missing semicolon.
SQL
var x int
var x int
Correct.
Go
<center>value</center>
<div style='text-align:center;'>value</div>
Use CSS.
HTML
val val: Int = 'message'
val val: String = 'message'
Fix type.
Kotlin
val z = 26; z = 7
var z = 26; z = 7
Use var for reassignment.
Scala
object Product {{ def main(args: Array[String]) = println("output") }}
object Product {{ def main(args: Array[String]): Unit = println("output") }}
Add return type Unit.
Scala
function test(item:string){{return item;}} test(36);
function test(item:string){{return item;}} test('test');
Pass correct type.
TypeScript
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
if foo = 19
if foo == 19
Use ==.
MATLAB
items[76]
if (items.indices.contains(76)) items[76]
Check index.
Kotlin
print('test')
print('test')
Correct.
R
print 'result'
print 'result';
Add semicolon.
Perl
jwt.sign({{id:76}}, 'password');
jwt.sign({{id:76}}, 'password', {{expiresIn:'2h'}});
Add expiration.
Node.js
let data = 41; let data = 33;
let data = 41; data = 33;
Duplicate declaration.
JavaScript
echo 'message'
echo 'message';
Add semicolon.
PHP
b = world
b = 'world'
Quote strings.
Python
p {{ color: blue }}
p {{ color: blue; }}
Add semicolon.
CSS
console.log('world'
console.log('world')
Close parenthesis.
JavaScript
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
x > 26 & b < 4
x > 26 and b < 4
Use 'and' not '&'.
Python
var y int = 'hello'
var y string = 'hello'
Type mismatch.
Go