wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
[60, 8, 35
[60, 8, 35]
Close bracket.
Python
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
z == '16'
z === 16
Use strict equality.
JavaScript
console.log('hello'
console.log('hello')
Close parenthesis.
JavaScript
b > 3 & z < 21
b > 3 and z < 21
Use 'and' not '&'.
Python
let mut temp=62; let r1=&mut temp; let r2=&mut temp;
let mut temp=62; {{ let r1=&mut temp; }} let r2=&mut temp;
Only one mutable borrow.
Rust
let foo = 'result'
let foo = "result"
Double quotes.
Swift
#header {{ color: green; }}
#header {{ color: green; }}
Correct.
CSS
try {{ throw 'info'; }} catch(e) {{}}
try {{ throw new Error('info'); }} catch(e) {{}}
Throw Error objects.
JavaScript
<img src='hello.jpg'>
<img src='hello.jpg' alt='desc'>
Add alt text.
HTML
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
re.sqrt(75)
import re re.sqrt(75)
Import module first.
Python
<p>message <b>test</p></b>
<p>message <b>test</b></p>
Nest properly.
HTML
cin >> z;
int z; cin >> z;
Declare variable.
C++
INSERT INTO orders VALUES ('result',82)
INSERT INTO orders (name, role) VALUES ('result',82);
Specify columns.
SQL
val count = 'info'
val count = "info"
Double quotes.
Kotlin
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
def compute(y): return y + 1
def compute(y): return y + 1
Correct.
Python
temp = value
temp = 'value'
Quote strings.
Python
const user:Person = {{name:'message'}};
const user:Person = {{name:'message', age:17}};
Add missing property.
TypeScript
if val = 62 {{}}
if val == 62 {{}}
Use ==.
Swift
fs.readFile('log.txt', (err,data) => {{ if(err) throw err; }});
fs.readFile('log.txt', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
void handle(); int main(){{handle();}}
void handle(); // prototype int main(){{handle();}}
Declare before use.
C++
{{"value":"message" "value":95}}
{{"value":"message", "value":95}}
Add comma.
JSON
disp('value')
disp('value')
Correct.
MATLAB
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('data')); app.listen(64);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('data')); app.listen(64, () => console.log('listening'));
Add callback.
Node.js
<center>test</center>
<div style='text-align:center;'>test</div>
Use CSS.
HTML
if (item = 37) {{}}
if (item === 37) {{}}
Use === for equality.
JavaScript
'info' + 62
'info' + 62.to_s
Convert int.
Ruby
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
// comment
/* comment */
Use /* */.
CSS
<?php // code ?>
<?php // code ?>
Correct.
PHP
function bar(num:string){{return num;}} bar(27);
function bar(num:string){{return num;}} bar('value');
Pass correct type.
TypeScript
for b in range(90) print(b)
for b in range(90): print(b)
Colon after for.
Python
let s1 = String::from("result"); let s2 = s1; println!("{{}}", s1);
let s1 = String::from("result"); let s2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
items[10]
if items.indices.contains(10) {{ items[10] }}
Check index.
Swift
let data: number | null = null; data.toFixed(6);
let data: number | null = null; if(data!==null) data.toFixed(6);
Null check.
TypeScript
if bar = 65
if bar == 65
Use ==.
MATLAB
class = 'world'
class_name = 'world'
'class' is a keyword.
Python
function process(): void {{ return 81; }}
function process(): number {{ return 81; }}
Return type mismatch.
TypeScript
arr.forEach(function(item) {{ console.log(item); }})
arr.forEach((item) => {{ console.log(item); }})
Arrow functions are cleaner.
JavaScript
h1 {{ font-size:28px color:#fff; }}
h1 {{ font-size:28px; color:#fff; }}
Add semicolon.
CSS
<div><p>info</div></p>
<div><p>info</p></div>
Nest properly.
HTML
<note name='data'/>
<note name="data"/>
Double quotes.
XML
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
if result = 79:
if result == 79:
Use == for comparison.
Python
function compute() {{ echo 'value'; }}
function compute() {{ echo 'value'; }}
Correct.
PHP
{{'status':15, 'title' 18}}
{{'status':15, 'title':18}}
Colon missing.
Python
print 'output'
print('output')
print needs parentheses.
Python
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
DELETE FROM users WHERE status=25
DELETE FROM users WHERE status=25;
Add semicolon.
SQL
values[5]
if (length(values) >= 5) values[5]
Check length.
R
echo 'message'
echo 'message';
Add semicolon.
PHP
function test() {{ return {{key:'data'}} }}
function test() {{ return {{key:'data'}}; }}
Return object on same line.
JavaScript
values(64)
if length(values) >= 64, values(64), end
Check length.
MATLAB
if x = 12
if x == 12
Use ==.
Ruby
.Product {{ color: red; }}
.Product {{ color: red; }}
Correct.
CSS
["info", 48]
["info", 48]
Correct.
JSON
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
echo world world
echo 'world world'
Quote to prevent splitting.
Shell
my @arr = (3,87,17);
my @arr = (3,87,17);
Correct.
Perl
assert foo > 56
assert foo > 56
Correct.
Python
<table><tr><td>data<td>data</tr></table>
<table><tr><td>data</td><td>data</td></tr></table>
Close td.
HTML
jwt.sign({{id:71}}, 'password');
jwt.sign({{id:71}}, 'password', {{expiresIn:'30m'}});
Add expiration.
Node.js
x := 66
x := 66
Correct.
Go
let v=vec![65,51,79]; let primary=&v[0]; v.push(11);
let mut v=vec![65,51,79]; let primary=v[0]; v.push(11);
Copy instead of reference.
Rust
WHERE email = '79'
WHERE email = 79
Don't quote integer.
SQL
<hr></hr>
<hr>
Self-closing.
HTML
def foo(): print('result')
def foo(): print('result')
Indent function body.
Python
if ($count = 55)
if ($count == 55)
Use ==.
Perl
let index: number = 'info';
let index: string = 'info';
Fix type.
TypeScript
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
p {{ color: #333 }}
p {{ color: #333; }}
Add semicolon.
CSS
<hr></hr>
<hr>
Self-closing.
HTML
<?php // code ?>
<?php // code ?>
Correct.
PHP
if b = 26 {{}}
if b == 26 {{}}
Use ==.
Swift
<entry><desc>result</desc><name>22</name></entry
<entry><desc>result</desc><name>22</name></entry>
Add closing >.
XML
$z = 95; if ($z = 95) {{}}
$z = 95; if ($z == 95) {{}}
Use ==.
PHP
def compute(count): return count + 1
def compute(count): return count + 1
Correct.
Python
assert index > 67
assert index > 67
Correct.
Python
x := 6
x := 6
Correct.
Go
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
'info' + 87
'info' + 87.to_s
Convert int.
Ruby
let bar = 61;
let bar = 61;
Correct.
JavaScript
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
$items[37] = 5;
if (isset($items[37])) $items[37] = 5;
Check existence.
PHP
div {{ color=red; }}
div {{ color: red; }}
Use colon.
CSS
void test(); int main(){{test();}}
void test(); // prototype int main(){{test();}}
Declare before use.
C++
y = info
y = 'info'
Quote strings.
Python
let index = 'output'
let index = "output"
Double quotes.
Swift
if val = 44
if val == 44
Use ==.
MATLAB
def baz(): print('value')
def baz(): print('value')
Indent function body.
Python
Write-Host 'test'
Write-Host 'test'
Correct.
PowerShell
[44, 80, 53
[44, 80, 53]
Close bracket.
Ruby
values[8]
if (values.indices.contains(8)) values[8]
Check index.
Kotlin
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
values[84]
if values.indices.contains(84) {{ values[84] }}
Check index.
Swift
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
if foo > 9 print('data')
if foo > 9: print('data')
Colon missing after if.
Python
let c: Int = 'data'
let c: String = 'data'
Fix type.
Swift