Use
const declarations for variables that are never reassigned JS-0242
Anti-pattern
Minor
a year ago
—
2 years old
'p' is never reassigned. Use 'const' instead
17
18
19function main() {
20 let p = [];21 generatePrimes(p, 1e6);
22 return p[10000];
23};'IsPrime' is never reassigned. Use 'const' instead
1function generatePrimes(primes, MAX_SIZE){
2 let IsPrime = Array(MAX_SIZE).fill(true); 3
4 let p,i;
5 for (p = 2; p * p < MAX_SIZE;p++) {'reversed' is never reassigned. Use 'const' instead
2 let nray = Array.from(
3 String(n), (i) => (Number(i))
4 );
5 let reversed = nray.reverse(); 6
7
8 return String(n) === reversed.join("");'n' is never reassigned. Use 'const' instead
9};
10
11function main() {
12 let n = [];13 for (let i = 100; i < 1000; i++ ) {
14 for (let j = 100; j < 1000; j++) {
15 let k = i * j;'k' is never reassigned. Use 'const' instead
12 let n = [];
13 for (let i = 100; i < 1000; i++ ) {
14 for (let j = 100; j < 1000; j++) {
15 let k = i * j;16 if (isPalendromic(k)) {
17 n.push(k);
18 };
Description
Variables that are never re-assigned a new value after their initial declaration should be declared with the const keyword.
This prevents the programmer from erroneously re-assigning to a read-only variable, and informs those reading the code that a variable is a constant value.
Bad Practice
let pi = Math.PI
for (let x of xs) {
use(x);
}
let { a, b } = object;
use(a, b);
Recommended
const pi = Math.PI
for (const x of xs) {
use(x);
}
const { a, b } = object;
use(a, b);