Eslint plugin to enforce code style of reassignment and update expressions
Install package.
npm install eslint-plugin-assignment --save-dev
In .eslintrc
"plugins": [
"assignment"
],
"rules": {
"assignment/no-expression": "error"
}
no-expression
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.
compound
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.
increment
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.
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.