max-params-function-assign

Daniel StrongError ProneInformational

No tags

No CWE or CVE

This rule warns once a function has five parameters because this can be difficult to maintain.

If you need this many parameters, you might be better off combining the parameters into an object or splitting your function.

Ast Rule: assignment

max-params-function-assign

How to write a rule

const MAX_PARAMS = 5;

function visit(node, filename, code) {
  if (!node || !node.right) return;
	
	// if the right side isn't a function, skip it
  if (node.right.astType !== 'functiondefinition') return;
  
	// if the function doesn't have an parameters, skip it
	if (!node.right.parameters) return;
	
	// if the function has less than the max, skip it
  if (node.right.parameters?.values.length < MAX_PARAMS) return;

  const error = buildError(
    node.right.parameters.start.line,
    node.right.parameters.start.col,
    node.right.parameters.end.line,
    node.right.parameters.end.col,
    `Having this many parameters can be difficult to manage. Consider splitting this function.`,
    "INFORMATIONAL",
    "BEST_PRACTICES"
  );

  addError(error);
}

unacceptable.js

Expected test result: has error

Function expressions with too many parameters

const a = (foo, bar, baz, qux, fred) => {};
const b = (foo, bar, baz, qux, fred, thud) => {};
const c = function(foo, bar, baz, qux, fred) {};
const d = function(foo, bar, baz, qux, fred, thud) {};

acceptable.js

Expected test result: no error

Function expressions with an acceptable number of parameters

const a = () => {};
const b = (foo) => {};
const c = (foo, bar) => {};
const d = (foo, bar, baz) => {};
const e = (foo, bar, baz, qux) => {};
const f = function() {};
const g = function(foo) {};
const h = function(foo, bar) {};
const i = function(foo, bar, baz) {};
const j = function(foo, bar, baz, qux) {};

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