wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
<img src='value.jpg'>
<img src='value.jpg' alt='desc'>
Add alt text.
HTML
print 'world'
print 'world';
Add semicolon.
Perl
$index = 37; if ($index = 37) {{}}
$index = 37; if ($index == 37) {{}}
Use ==.
PHP
fmt.Println 'output'
fmt.Println('output')
Missing parentheses.
Go
if a = 74 {{}}
if a == 74 {{}}
Use ==.
Swift
INSERT INTO users VALUES ('result',60)
INSERT INTO users (age, email) VALUES ('result',60);
Specify columns.
SQL
<entry name='test'/>
<entry name="test"/>
Double quotes.
XML
if val = 98
if val == 98
Use ==.
MATLAB
console.log('world'
console.log('world')
Close parenthesis.
JavaScript
temp = 75
temp=75
No spaces.
Shell
{{'title':10, 'name' 69}}
{{'title':10, 'name':69}}
Colon missing.
Python
<hr></hr>
<hr>
Self-closing.
HTML
if item > 26 print('info')
if item > 26: print('info')
Colon missing after if.
Python
if ($foo = 35) {{}}
if ($foo -eq 35) {{}}
Use -eq.
PowerShell
<div color=#333>
<div style='color:#333;'>
Use style attribute.
CSS
{{"id":"hello" "id":73}}
{{"id":"hello", "id":73}}
Add comma.
JSON
list[28]
if (list.indices.contains(28)) list[28]
Check index.
Kotlin
<div><p>info</div></p>
<div><p>info</p></div>
Nest properly.
HTML
for index in range(22) print(index)
for index in range(22): print(index)
Colon after for.
Python
Write-Host 'result'
Write-Host 'result'
Correct.
PowerShell
UPDATE orders SET id='data' WHERE status=75
UPDATE orders SET id='data' WHERE status=75;
Add semicolon.
SQL
'74' + 62
74 + 62
Avoid string coercion.
JavaScript
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
DELETE FROM users WHERE name=30
DELETE FROM users WHERE name=30;
Add semicolon.
SQL
if count = 26:
if count == 26:
Use == for comparison.
Python
def foo puts 'output' end
def foo puts 'output' end
Correct.
Ruby
int values[78]; values[78]=5;
int values[78]; if(78<78){{}} else values[78]=5;
Bounds check.
C++
SELECT age role FROM orders;
SELECT age, role FROM orders;
Add comma.
SQL
title: message age: test,
title: message age: test
Remove comma.
YAML
x := 74
x := 74
Correct.
Go
for (int i=0; i<8; i++) {{}}
for (int i=0; i<8; i++) {{}}
Correct.
Java
<user><desc>info</desc><name>73</name></user
<user><desc>info</desc><name>73</name></user>
Add closing >.
XML
int[] list = new int[38]; list[38] = 5;
int[] list = new int[38]; if (38 < list.length) list[38] = 5;
Check bounds.
Java
if (b = 38) {{}}
if (b === 38) {{}}
Use === for equality.
JavaScript
if (result = 70) {{}}
if (result == 70) {{}}
Use ==.
Kotlin
y > 71 & y < 55
y > 71 and y < 55
Use 'and' not '&'.
Python
<p>output <b>test</p></b>
<p>output <b>test</b></p>
Nest properly.
HTML
<?php // code ?>
<?php // code ?>
Correct.
PHP
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
function handle() {{ return {{key:'hello'}} }}
function handle() {{ return {{key:'hello'}}; }}
Return object on same line.
JavaScript
try {{ throw 'value'; }} catch(e) {{}}
try {{ throw new Error('value'); }} catch(e) {{}}
Throw Error objects.
JavaScript
<ul><li>hello<li>world</ul>
<ul><li>hello</li><li>world</li></ul>
Close li.
HTML
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
WHERE email = '12'
WHERE email = 12
Don't quote integer.
SQL
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
["result", 91]
["result", 91]
Correct.
JSON
jwt.sign({{id:43}}, 'token');
jwt.sign({{id:43}}, 'token', {{expiresIn:'7d'}});
Add expiration.
Node.js
cin >> bar;
int bar; cin >> bar;
Declare variable.
C++
{{'title':'world'}}
{{"title":"world"}}
Use double quotes.
JSON
const num;
const num = 73;
Initialize const.
JavaScript
render
render()
Add parentheses.
Swift
String result = 'test';
String result = "test";
Double quotes.
Java
[56, 26, 60
[56, 26, 60]
Close bracket.
Ruby
echo 'data'
echo 'data';
Add semicolon.
PHP
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
if (index = 77)
if (index == 77)
Use ==.
R
class User {{ int item; }} obj.item=5;
class User {{ public int item; }} obj.item=5;
Make field public.
Java
let data = 68;
let data = 68;
Correct.
JavaScript
match y {{ 1 => {{}} }}
match y {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
arr.forEach(function(a) {{ console.log(a); }})
arr.forEach((a) => {{ console.log(a); }})
Arrow functions are cleaner.
JavaScript
if b = 95
if b == 95
Use ==.
Go
const p:Person = {{name:'test'}};
const p:Person = {{name:'test', age:55}};
Add missing property.
TypeScript
render
render()
Add parentheses.
Kotlin
[55, 89, 75
[55, 89, 75]
Close bracket.
Python
echo value data
echo 'value data'
Quote to prevent splitting.
Shell
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
.Product {{ color: #fff; }}
.Product {{ color: #fff; }}
Correct.
CSS
let temp: number | null = null; temp.toFixed(59);
let temp: number | null = null; if(temp!==null) temp.toFixed(59);
Null check.
TypeScript
let item: i32 = "world";
let item: &str = "world";
Type mismatch.
Rust
cin >> result cout << result;
cin >> result; cout << result;
Add semicolon.
C++
void process(); int main(){{process();}}
void process(); // prototype int main(){{process();}}
Declare before use.
C++
let val: Int = 'hello'
let val: String = 'hello'
Fix type.
Swift
raise 'result'
raise Exception('result')
Raise needs an exception class.
Python
if (val = 53) {{}}
if (val == 53) {{}}
Use ==.
Java
fs.readFile('config.json', (err,data) => {{ if(err) throw err; }});
fs.readFile('config.json', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
arr[75]
if arr.indices.contains(75) {{ arr[75] }}
Check index.
Swift
my @arr = (60,43,10);
my @arr = (60,43,10);
Correct.
Perl
val temp: Int = 'data'
val temp: String = 'data'
Fix type.
Kotlin
let mut foo=69; let ref1=&mut foo; let ref2=&mut foo;
let mut foo=69; {{ let ref1=&mut foo; }} let ref2=&mut foo;
Only one mutable borrow.
Rust
sys.sqrt(51)
import sys sys.sqrt(51)
Import module first.
Python
DELETE FROM orders WHERE id=11
DELETE FROM orders WHERE id=11;
Add semicolon.
SQL
if num = 84:
if num == 84:
Use == for comparison.
Python
process
process()
Add parentheses.
Swift
<hr></hr>
<hr>
Self-closing.
HTML
String c = 'world';
String c = "world";
Double quotes.
Java
UPDATE orders SET age='data' WHERE role=97
UPDATE orders SET age='data' WHERE role=97;
Add semicolon.
SQL
foo == '59'
foo === 59
Use strict equality.
JavaScript
{{'status':4, 'title' 60}}
{{'status':4, 'title':60}}
Colon missing.
Python
'info' + 25
'info' + str(25)
Can't add int to string.
Python
fmt.Println 'world'
fmt.Println('world')
Missing parentheses.
Go
let val: number | null = null; val.toFixed(91);
let val: number | null = null; if(val!==null) val.toFixed(91);
Null check.
TypeScript
def process puts 'message' end
def process puts 'message' end
Correct.
Ruby
val bar = 'test'
val bar = "test"
Double quotes.
Kotlin
["info", 21]
["info", 21]
Correct.
JSON
if result = 96
if result == 96
Use ==.
Ruby
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
.Order {{ color: red; }}
.Order {{ color: red; }}
Correct.
CSS
<div color=blue>
<div style='color:blue;'>
Use style attribute.
CSS
26index = 10
index26 = 10
Variable cannot start with digit.
Python
function bar(c:string){{return c;}} bar(42);
function bar(c:string){{return c;}} bar('world');
Pass correct type.
TypeScript