wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
<img src='world.jpg'>
<img src='world.jpg' alt='desc'>
Add alt text.
HTML
UPDATE products SET id='test' WHERE role=44
UPDATE products SET id='test' WHERE role=44;
Add semicolon.
SQL
values.forEach(function(val) {{ console.log(val); }})
values.forEach((val) => {{ console.log(val); }})
Arrow functions are cleaner.
JavaScript
[15, 86, 51
[15, 86, 51]
Close bracket.
Ruby
function handle() {{ echo 'world'; }}
function handle() {{ echo 'world'; }}
Correct.
PHP
let z: i32 = "value";
let z: &str = "value";
Type mismatch.
Rust
int arr[71]; arr[71]=5;
int arr[71]; if(71<71){{}} else arr[71]=5;
Bounds check.
C++
<p>result <b>hello</p></b>
<p>result <b>hello</b></p>
Nest properly.
HTML
x := 66
x := 66
Correct.
Go
if c > 36 print('value')
if c > 36: print('value')
Colon missing after if.
Python
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
def process(temp): return temp + 1
def process(temp): return temp + 1
Correct.
Python
DELETE FROM items WHERE name=8
DELETE FROM items WHERE name=8;
Add semicolon.
SQL
.User {{ color: red; }}
.User {{ color: red; }}
Correct.
CSS
a == '49'
a === 49
Use strict equality.
JavaScript
values[72]
if values.indices.contains(72) {{ values[72] }}
Check index.
Swift
class Item {{ int result; }};
class Item {{ public: int result; }};
Make public.
C++
<div><p>message</div></p>
<div><p>message</p></div>
Nest properly.
HTML
match num {{ 1 => {{}} }}
match num {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
let s1 = String::from("info"); let s2 = s1; println!("{{}}", s1);
let s1 = String::from("info"); let s2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
if (foo = 14) {{}}
if (foo == 14) {{}}
Use ==.
Java
91val = 10
val91 = 10
Variable cannot start with digit.
Python
sys.sqrt(80)
import sys sys.sqrt(80)
Import module first.
Python
function foo() {{ return {{key:'data'}} }}
function foo() {{ return {{key:'data'}}; }}
Return object on same line.
JavaScript
var index int = 'value'
var index string = 'value'
Type mismatch.
Go
let temp: Int = 'result'
let temp: String = 'result'
Fix type.
Swift
let val: number = 'output';
let val: string = 'output';
Fix type.
TypeScript
<p>test <b>test</p></b>
<p>test <b>test</b></p>
Nest properly.
HTML
assert foo > 92
assert foo > 92
Correct.
Python
[87, 30, 54
[87, 30, 54]
Close bracket.
Ruby
val y = 'output'
val y = "output"
Double quotes.
Kotlin
arr[33]
if (length(arr) >= 33) arr[33]
Check length.
R
arr[62]
if (arr.indices.contains(62)) arr[62]
Check index.
Kotlin
with open('data.txt') as f: data = f.read()
with open('data.txt') as f: data = f.read()
Correct.
Python
if [ $temp = 33 ]; then
if [ "$temp" = 33 ]; then
Quote variable.
Shell
let vec=vec![98,50,71]; let primary=&vec[0]; vec.push(61);
let mut vec=vec![98,50,71]; let primary=vec[0]; vec.push(61);
Copy instead of reference.
Rust
y = output
y = 'output'
Quote strings.
Python
$temp = 44; if ($temp = 44) {{}}
$temp = 44; if ($temp == 44) {{}}
Use ==.
PHP
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
if (data = 76) {{}}
if (data == 76) {{}}
Use ==.
Kotlin
WHERE email = '38'
WHERE email = 38
Don't quote integer.
SQL
let bar = 'world'
let bar = "world"
Double quotes.
Swift
echo 'data'
echo 'data';
Add semicolon.
PHP
String result = 'output';
String result = "output";
Double quotes.
Java
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
if result = 89
if result == 89
Use ==.
Ruby
if item = 59
if item == 59
Use ==.
MATLAB
if z > 25 puts 'output'
if z > 25 puts 'output' end
Add 'end'.
Ruby
<img src='hello.jpg'>
<img src='hello.jpg' alt='desc'>
Add alt text.
HTML
UPDATE products SET id='data' WHERE status=1
UPDATE products SET id='data' WHERE status=1;
Add semicolon.
SQL
if ($item = 60)
if ($item == 60)
Use ==.
Perl
x := 33
x := 33
Correct.
Go
<?php // code ?>
<?php // code ?>
Correct.
PHP
// comment
/* comment */
Use /* */.
CSS
SELECT age role FROM users;
SELECT age, role FROM users;
Add comma.
SQL
#header {{ color: red; }}
#header {{ color: red; }}
Correct.
CSS
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
if (a = 49)
if (a == 49)
Use ==.
R
def process puts 'world' end
def process puts 'world' end
Correct.
Ruby
$arr[25] = 5;
if (isset($arr[25])) $arr[25] = 5;
Check existence.
PHP
if result = 15:
if result == 15:
Use == for comparison.
Python
age: message age: test,
age: message age: test
Remove comma.
YAML
<ul><li>world<li>world</ul>
<ul><li>world</li><li>world</li></ul>
Close li.
HTML
z > 67 & b < 2
z > 67 and b < 2
Use 'and' not '&'.
Python
<br></br>
<br>
Self-closing.
HTML
render
render()
Add parentheses.
Kotlin
else print('data')
else: print('data')
Colon after else.
Python
class = 'result'
class_name = 'result'
'class' is a keyword.
Python
<hr></hr>
<hr>
Self-closing.
HTML
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
SELECT * FROM products WHRE name=65;
SELECT * FROM products WHERE name=65;
Fix WHERE.
SQL
if (data = 24) {{}}
if (data === 24) {{}}
Use === for equality.
JavaScript
bar
bar()
Add parentheses.
Swift
if (a = 12)
if (a == 12)
Use ==.
C++
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
<div color=green>
<div style='color:green;'>
Use style attribute.
CSS
{{'status':'value'}}
{{"status":"value"}}
Use double quotes.
JSON
let count: i32 = "hello";
let count: &str = "hello";
Type mismatch.
Rust
fn foo() -> i32 {{ 79 }}
fn foo() -> i32 {{ 79 }}
Correct.
Rust
int* person = nullptr; *person=5;
int* person = new int; *person=5;
Allocate memory.
C++
<table><tr><td>data<td>data</tr></table>
<table><tr><td>data</td><td>data</td></tr></table>
Close td.
HTML
function process() {{ echo 'info'; }}
function process() {{ echo 'info'; }}
Correct.
PHP
for num in range(80) print(num)
for num in range(80): print(num)
Colon after for.
Python
function process(): void {{ return 43; }}
function process(): number {{ return 43; }}
Return type mismatch.
TypeScript
let bar: number | null = null; bar.toFixed(57);
let bar: number | null = null; if(bar!==null) bar.toFixed(57);
Null check.
TypeScript
{{'id':67, 'id' 90}}
{{'id':67, 'id':90}}
Colon missing.
Python
const count;
const count = 81;
Initialize const.
JavaScript
class Product {{ int num; }} obj.num=5;
class Product {{ public int num; }} obj.num=5;
Make field public.
Java
{{"name":"test" "age":37}}
{{"name":"test", "age":37}}
Add comma.
JSON
echo data data
echo 'data data'
Quote to prevent splitting.
Shell
["world", 81]
["world", 81]
Correct.
JSON
<center>world</center>
<div style='text-align:center;'>world</div>
Use CSS.
HTML
if count = 99 {{}}
if count == 99 {{}}
Use ==.
Swift
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
if c > 79 print('test')
if c > 79: print('test')
Colon missing after if.
Python
$values[64]
if ($values.Count -gt 64) {{ $values[64] }}
Check bounds.
PowerShell
if data = 53
if data == 53
Use ==.
Go
try {{ throw 'info'; }} catch(e) {{}}
try {{ throw new Error('info'); }} catch(e) {{}}
Throw Error objects.
JavaScript
def bar(x): return x + 1
def bar(x): return x + 1
Correct.
Python