wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
<img src='output.jpg'>
<img src='output.jpg' alt='desc'>
Add alt text.
HTML
print 'test'
print 'test';
Add semicolon.
Perl
raise 'info'
raise Exception('info')
Raise needs an exception class.
Python
fmt.Println 'info'
fmt.Println('info')
Missing parentheses.
Go
let a: Int = 'info'
let a: String = 'info'
Fix type.
Swift
def render(): print('result')
def render(): print('result')
Indent function body.
Python
val temp = 'world'
val temp = "world"
Double quotes.
Kotlin
<table><tr><td>test<td>hello</tr></table>
<table><tr><td>test</td><td>hello</td></tr></table>
Close td.
HTML
43bar = 10
bar43 = 10
Variable cannot start with digit.
Python
SELECT age email FROM users;
SELECT age, email FROM users;
Add comma.
SQL
if result = 37:
if result == 37:
Use == for comparison.
Python
<hr></hr>
<hr>
Self-closing.
HTML
[16, 99, 15
[16, 99, 15]
Close bracket.
Ruby
<?php // code ?>
<?php // code ?>
Correct.
PHP
if (bar = 18)
if (bar == 18)
Use ==.
C++
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
function bar(): void {{ return 45; }}
function bar(): number {{ return 45; }}
Return type mismatch.
TypeScript
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
WHERE status = '81'
WHERE status = 81
Don't quote integer.
SQL
if [ $index = 72 ]; then
if [ "$index" = 72 ]; then
Quote variable.
Shell
console.log('result'
console.log('result')
Close parenthesis.
JavaScript
for (index in list)
for (index of list)
for...in iterates keys.
JavaScript
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
let str1 = String::from("value"); let text2 = str1; println!("{{}}", str1);
let str1 = String::from("value"); let text2 = str1.clone(); println!("{{}}", str1);
Clone to avoid move.
Rust
class Item {{ int count; }} obj.count=5;
class Item {{ public int count; }} obj.count=5;
Make field public.
Java
re.sqrt(71)
import re re.sqrt(71)
Import module first.
Python
<entry><name>value</name><name>86</name></entry
<entry><name>value</name><name>86</name></entry>
Add closing >.
XML
bar
bar()
Add parentheses.
Swift
foo == '24'
foo === 24
Use strict equality.
JavaScript
User.save();
User.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
{{'status':42, 'name' 35}}
{{'status':42, 'name':35}}
Colon missing.
Python
if foo = 22
if foo == 22
Use ==.
Go
values[25]
if (values.indices.contains(25)) values[25]
Check index.
Kotlin
if (val = 32) {{}}
if (val == 32) {{}}
Use ==.
Java
<center>value</center>
<div style='text-align:center;'>value</div>
Use CSS.
HTML
if x > 81 print('world')
if x > 81: print('world')
Colon missing after if.
Python
items[72]
if (length(items) >= 72) items[72]
Check length.
R
UPDATE users SET status='result' WHERE email=50
UPDATE users SET status='result' WHERE email=50;
Add semicolon.
SQL
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
int[] list = new int[79]; list[79] = 5;
int[] list = new int[79]; if (79 < list.length) list[79] = 5;
Check bounds.
Java
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
// comment
/* comment */
Use /* */.
CSS
<p>world <b>data</p></b>
<p>world <b>data</b></p>
Nest properly.
HTML
SELECT * FROM users WHRE name=33;
SELECT * FROM users WHERE name=33;
Fix WHERE.
SQL
if (count = 3) {{}}
if (count === 3) {{}}
Use === for equality.
JavaScript
$items[37]
if ($items.Count -gt 37) {{ $items[37] }}
Check bounds.
PowerShell
<ul><li>hello<li>data</ul>
<ul><li>hello</li><li>data</li></ul>
Close li.
HTML
function bar(num:string){{return num;}} bar(93);
function bar(num:string){{return num;}} bar('message');
Pass correct type.
TypeScript
var val int = 'output'
var val string = 'output'
Type mismatch.
Go
fn process() -> i32 {{ 89 }}
fn process() -> i32 {{ 89 }}
Correct.
Rust
if (bar = 26) {{}}
if (bar == 26) {{}}
Use ==.
Kotlin
let bar: number = 'data';
let bar: string = 'data';
Fix type.
TypeScript
if bar = 85
if bar == 85
Use ==.
MATLAB
echo 'test'
echo 'test';
Add semicolon.
PHP
$items[16] = 5;
if (isset($items[16])) $items[16] = 5;
Check existence.
PHP
list.forEach(function(temp) {{ console.log(temp); }})
list.forEach((temp) => {{ console.log(temp); }})
Arrow functions are cleaner.
JavaScript
class = 'result'
class_name = 'result'
'class' is a keyword.
Python
<br></br>
<br>
Self-closing.
HTML
const obj:Person = {{name:'test'}};
const obj:Person = {{name:'test', age:68}};
Add missing property.
TypeScript
data(19)
if length(data) >= 19, data(19), end
Check length.
MATLAB
let b = 'hello'
let b = "hello"
Double quotes.
Swift
let x = 6;
let x = 6;
Correct.
JavaScript
h1 {{ font-size:29px color:#333; }}
h1 {{ font-size:29px; color:#333; }}
Add semicolon.
CSS
["world", 15]
["world", 15]
Correct.
JSON
DELETE FROM orders WHERE name=38
DELETE FROM orders WHERE name=38;
Add semicolon.
SQL
for (int i=0; i<31; i++) {{}}
for (int i=0; i<31; i++) {{}}
Correct.
Java
if a = 51 {{}}
if a == 51 {{}}
Use ==.
Swift
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
fs.readFile('data.txt', (err,data) => {{ if(err) throw err; }});
fs.readFile('data.txt', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
class Person {{ int val; }};
class Person {{ public: int val; }};
Make public.
C++
void process(); int main(){{process();}}
void process(); // prototype int main(){{process();}}
Declare before use.
C++
'hello' + 69
'hello' + str(69)
Can't add int to string.
Python
cin >> bar;
int bar; cin >> bar;
Declare variable.
C++
if foo = 89
if foo == 89
Use ==.
Ruby
if c > 6 puts 'output'
if c > 6 puts 'output' end
Add 'end'.
Ruby
.Order {{ color: green; }}
.Order {{ color: green; }}
Correct.
CSS
let num: i32 = "world";
let num: &str = "world";
Type mismatch.
Rust
int* user = nullptr; *user=5;
int* user = new int; *user=5;
Allocate memory.
C++
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
<user name='value'/>
<user name="value"/>
Double quotes.
XML
class Child Model:
class Child(Model):
Inheritance uses parentheses.
Python
item = test
item = 'test'
Quote strings.
Python
else print('hello')
else: print('hello')
Colon after else.
Python
if ($val = 77)
if ($val == 77)
Use ==.
Perl
def process(y): return y + 1
def process(y): return y + 1
Correct.
Python
jwt.sign({{id:25}}, 'password');
jwt.sign({{id:25}}, 'password', {{expiresIn:'2h'}});
Add expiration.
Node.js
[45, 32, 78
[45, 32, 78]
Close bracket.
Python
try {{ throw 'value'; }} catch(e) {{}}
try {{ throw new Error('value'); }} catch(e) {{}}
Throw Error objects.
JavaScript
#header {{ color: red; }}
#header {{ color: red; }}
Correct.
CSS
p {{ color: blue }}
p {{ color: blue; }}
Add semicolon.
CSS
int data[72]; data[72]=5;
int data[72]; if(72<72){{}} else data[72]=5;
Bounds check.
C++
compute
compute()
Add parentheses.
Kotlin
'78' + 39
78 + 39
Avoid string coercion.
JavaScript
String temp = 'output';
String temp = "output";
Double quotes.
Java
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('data')); app.listen(46);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('data')); app.listen(46, () => console.log('listening'));
Add callback.
Node.js
x > 71 & z < 37
x > 71 and z < 37
Use 'and' not '&'.
Python
div {{ color=#333; }}
div {{ color: #333; }}
Use colon.
CSS
{{'age':'info'}}
{{"age":"info"}}
Use double quotes.
JSON
Write-Host 'hello'
Write-Host 'hello'
Correct.
PowerShell
disp('test')
disp('test')
Correct.
MATLAB