Using expressions to cause side-effects not allowed (no-expression-statement)

This rule checks that the value of an expression is assigned to a variable and thus helps promote side-effect free (pure) functions.

Rule Details

When you call a function and don’t use it’s return value, chances are high that it is being called for its side effect. e.g.

Examples of incorrect code for this rule:

/* eslint functional/no-expression-statement: "error" */

console.log("Hello world!");

/* eslint functional/no-expression-statement: "error" */

array.push(3);

/* eslint functional/no-expression-statement: "error" */

foo(bar);

Examples of correct code for this rule:

/* eslint functional/no-expression-statement: "error" */

const baz = foo(bar);

This rule accepts an options object of the following type:

{
  ignorePattern?: string | Array<string>;
}

The default options:

{
}

Patterns will be matched against the line(s) of code. See the ignorePattern docs for more information.