# functional/no-throw-statements 📝 Disallow throwing exceptions. 💼 This rule is enabled in the following configs: ☑️ `lite`,  `noExceptions`, ✅ `recommended`, 🔒 `strict`. 💭 This rule requires [type information](https://typescript-eslint.io/linting/typed-linting). This rule disallows the `throw` keyword. ## Rule Details Exceptions are not part of functional programming. As an alternative a function should return an error or in the case of an async function, a rejected promise. ### ❌ Incorrect ```js /* eslint functional/no-throw-statements: "error" */ throw new Error("Something went wrong."); ``` ### ✅ Correct ```js /* eslint functional/no-throw-statements: "error" */ function divide(x, y) { return y === 0 ? new Error("Cannot divide by zero.") : x / y; } ``` ```js /* eslint functional/no-throw-statements: "error" */ async function divide(x, y) { const [xv, yv] = await Promise.all([x, y]); return yv === 0 ? Promise.reject(new Error("Cannot divide by zero.")) : xv / yv; } ``` ## Options This rule accepts an options object of the following type: ```ts type Options = { allowToRejectPromises: boolean; }; ``` ### Default Options ```ts const defaults = { allowToRejectPromises: false, }; ``` ### Preset Overrides #### `recommended` and `lite` ```ts const recommendedAndLiteOptions = { allowToRejectPromises: true, }; ``` ### `allowToRejectPromises` If true, throw statements will be allowed when they are used to reject a promise, such when in an async function.\ This essentially allows throw statements to be used as return statements for errors. #### ✅ Correct ```js /* eslint functional/no-throw-statements: ["error", { "allowToRejectPromises": true }] */ async function divide(x, y) { const [xv, yv] = await Promise.all([x, y]); if (yv === 0) { throw new Error("Cannot divide by zero."); } return xv / yv; } ```