56 lines
1.8 KiB
Markdown
56 lines
1.8 KiB
Markdown
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---
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id: running-imperatively
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title: Running validations imperatively
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---
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express-validator favors the declarative way of doing things that express middlewares bring.
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This means most of the APIs _look and work better_ when simply passed into an express route handler.
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You can, however, give control of running these validations to your own middleware/route handler.
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This is possible with the use of the declarative method `run(req)`, available on both
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[validation chain](api-validation-chain.md#runreq-options) and [sanitization chains](api-sanitization-chain.md#runreq).
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Check the examples below to understand how this method can help you:
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## Example: standardized validation error response
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```js
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// can be reused by many routes
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const validate = validations => {
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return async (req, res, next) => {
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await Promise.all(validations.map(validation => validation.run(req)));
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const errors = validationResult(req);
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if (errors.isEmpty()) {
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return next();
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}
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res.status(400).json({ errors: errors.array() });
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};
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};
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app.post('/api/create-user', validate([
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body('email').isEmail(),
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body('password').isLength({ min: 6 })
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]), async (req, res, next) => {
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// request is guaranteed to not have any validation errors.
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const user = await User.create({ ... });
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});
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```
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## Example: validating with a condition
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```js
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app.post('/update-settings', [
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body('email').isEmail(),
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body('password').optional().isLength({ min: 6 })
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], async (req, res, next) => {
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// if a password has been provided, then a confirmation must also be provided.
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if (req.body.password) {
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await body('passwordConfirmation')
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.equals(req.body.password).withMessage('passwords do not match')
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.run(req);
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}
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// Check the validation errors, and update the user's settings.
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});
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```
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