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noParameterAssign

Diagnostic Category: lint/style/noParameterAssign

Since: v1.0.0

Sources:

Disallow reassigning function parameters.

Assignment to a function parameters can be misleading and confusing, as modifying parameters will also mutate the arguments object. It is often unintended and indicative of a programmer error.

In contrast to the ESLint rule, this rule cannot be configured to report assignments to a property of a parameter.

function f(param) {
param = 13;
}
code-block.js:2:5 lint/style/noParameterAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Reassigning a function parameter is confusing.

1 │ function f(param) {
> 2 │ param = 13;
^^^^^
3 │ }
4 │

The parameter is declared here:

> 1 │ function f(param) {
^^^^^
2 │ param = 13;
3 │ }

Use a local variable instead.

function f(param) {
param++;
}
code-block.js:2:5 lint/style/noParameterAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Reassigning a function parameter is confusing.

1 │ function f(param) {
> 2 │ param++;
^^^^^
3 │ }
4 │

The parameter is declared here:

> 1 │ function f(param) {
^^^^^
2 │ param++;
3 │ }

Use a local variable instead.

function f(param) {
for (param of arr) {}
}
code-block.js:2:10 lint/style/noParameterAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Reassigning a function parameter is confusing.

1 │ function f(param) {
> 2 │ for (param of arr) {}
^^^^^
3 │ }
4 │

The parameter is declared here:

> 1 │ function f(param) {
^^^^^
2 │ for (param of arr) {}
3 │ }

Use a local variable instead.

class C {
constructor(readonly prop: number) {
prop++
}
}
code-block.ts:3:9 lint/style/noParameterAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Reassigning a function parameter is confusing.

1 │ class C {
2 │ constructor(readonly prop: number) {
> 3 │ prop++
^^^^
4 │ }
5 │ }

The parameter is declared here:

1 │ class C {
> 2 │ constructor(readonly prop: number) {
^^^^^^^^^^^^
3 │ prop++
4 │ }

Use a local variable instead.

function f(param) {
let local = param;
}