constantAssignments

Reports attempting to reassign variables declared with const.

✅ This rule is included in the ts untyped presets.

The const keyword creates a read-only reference to a value, preventing reassignment. While properties of const objects and elements of const arrays can be mutated, the binding itself cannot be reassigned. Attempting to reassign a const variable results in a runtime error.

const 
const value: 1
value = 1;
const value: any
value = 2;

const 
const result: string
result = 
const getValue: () => string
getValue();
const result: any
result = 
const getOtherValue: () => string
getOtherValue();

const 
const counter: 0
counter = 0;
const counter: any
counter++;

const { 
const property: string
property } = 
const object: {
    property: string;
}
object;
const property: any
property = "new value";

for (const 
const item: string
item of 
const items: string[]
items) {
  
const item: any
item = 
const processItem: (item: string) => string
processItem(
const item: string
item);
}

let 
let value: number
value = 1;
let value: number
value = 2;

const 
const object: {
    value: number;
}
object = { 
value: number
value: 1 };
const object: {
    value: number;
}
object.
value: number
value = 2;

const 
const array: number[]
array = [1, 2, 3];
const array: number[]
array.
Array<number>.push(...items: number[]): number
Appends new elements to the end of an array, and returns the new length of the array.
@param ― items New elements to add to the array.
push(4);

const { 
const property: string
property } = 
const object: {
    property: string;
}
object;
var console: Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:

A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
@see ― source
console.
Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
@since ― v0.1.100
log(
const property: string
property);

for (let 
let item: string
item of 
const items: string[]
items) {
  
let item: string
item = 
const processItem: (item: string) => string
processItem(
let item: string
item);
}

Options

This rule is not configurable.

When Not To Use It

If your codebase relies on non-standard behavior that involves reassigning constant variables (which is highly discouraged), you might choose to disable this rule. For example, if you target a legacy runtime with non-standard JavaScript semantics, standard practices may not apply to you.

Equivalents in Other Linters

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constantAssignments

Examples

Options

When Not To Use It

Further Reading

Equivalents in Other Linters