eslint-plugin-assignment

Eslint plugin to enforce code style of reassignment and update expressions

Usage

Install package.

npm install eslint-plugin-assignment --save-dev

In .eslintrc

"plugins": [
  "assignment"
],
"rules": {
  "assignment/no-expression": "error"
}

Rules

Disallow use of reassignments and updates outside statements and voided expressions.

Examples of incorrect code for this rule:

const hasChanged = previous === (previous = current);

const setCurrent = (value) => (current = value);

Examples of correct code for this rule:

const hasChanged = previous === current;
previous = current;

const setCurrent = (value) => void (current = value);

This rule conflicts with no-cond-assign and no-return-assign. While this rule replaces the core functionality of both it does not offer an except-parens option.

Prefer compound reassignment expressions (e.g. i += 1) or verbose assignment expressions (e.g. i = i + 1) depending on options.

Set the prefer option to select which expressions to prefer. By default "compound" is preferred.

  "assignment/compound": ["warn", { "prefer": "compound" }]

  "assignment/compound": ["warn", { "prefer": "verbose" }]

Examples of incorrect code for this rule with "prefer": "compound":

i = i + 1;
i = i / 2;

Examples of correct code for this rule with "prefer": "compound":

i += 1;
i /= 2;

i++;

Examples of incorrect code for this rule with "prefer": "verbose":

i += 1;
i /= 2;

Examples of correct code for this rule with "prefer": "verbose":

i = i + 1;
i = i / 2;

i++;

This rule does not enforce the use of update expressions (e.g. i++). Use the rule assignment/increment for that.

This rule can automatically --fix violations either way by converting equivalent expressions.

Prefer compound assignment expressions (e.g. i += 1) or update expressions (e.g. i++) depending on options.

Set the prefer option to select which expressions to prefer. By default "compound" is preferred.

  "assignment/compound": ["warn", { "prefer": "compound" }]

  "assignment/compound": ["warn", { "prefer": "update" }]

Examples of incorrect code for this rule with "prefer": "compound":

i++;
--i;

Examples of correct code for this rule with "prefer": "compound":

i += 1;
i -= 1;

i = i + 1;

Examples of incorrect code for this rule with "prefer": "update":

i += 1;
i -= 1;

Examples of correct code for this rule with "prefer": "update":

++i;
i--;

i = i + 1;

This rule does not enforce the use of non-compound assignment expressions (e.g. i = i + 1). Use the rule assignment/compound for that.

Recommended use

Using assignment expressions outside statements can lead to confusing code or even bugs if the value of the expression is accidentally used. Enforcing assignment/no-expression solves that problem and is therefore recommended for all modern JavaScript projects.

assignment/compound and assignment/increment are opinionated and can be used to enforce any preference of syntax. Unless you want to prefer or ban a specific syntax don't enable these rules.

The recommended configuration enabled assignment/no-exression and disables assignment/compound and assignment/increment.