Why validate props in React
React props, which stands for “properties”, are read-only object being send from one component to another. Since Javascript is a dynamic language and doen’t have a built-in type checking solution, a component doen’t know props sent to it has correct type as it designed for. This can lead to bugs, or even worse, unexpected behaviors in a react app.
Many developers turned to TypeScript because it is a superset of Javascript and more important, it is strong typed. Fortunately, react has an internal mechanism for props type checking: PropTypes
Installation
Install the prop-types package via yarn or npm:
and import this package into project files:
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| import PropTypes from 'prop-types';
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Basic prop type validators
According to official docs, these are validators for the basic prop types:
- PropTypes.bool: The prop should be a Boolean
- PropTypes.number: The prop should be a number
- PropTypes.any: The prop can be of any data type
- PropTypes.string: The prop should be a string
- PropTypes.func: The prop should be a function
- PropTypes.array: The prop should be an array
- PropTypes.object: The prop should be an object
- PropTypes.symbol: The prop should be a symbol
- PropTypes.node: The prop should be anything that can be rendered by React
- ie. numbers, strings, elements can be rendered on screen, but not boolean
- PropTypes.element: The prop should be a React element
- PropTypes.any: The prop can be anything
Usage
Ensure a prop is an object with specified type of values
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| MyComponent.propTypes = {
objProp: PropTypes.shape({
id: PropTypes.number,
name: PropTypes.string,
productSize: PropTypes.oneOf(['S', 'M', 'L']),
birthdate: PropTypes.instanceOf(Date),
})
}
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Stric prop object matching
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| Component.propTypes = {
objProp: PropTypes.exact({
name: PropTypes.string,
age: PropTypes.number,
})
}
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Make a prop required
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| MyComponent.propTypes = {
propOne: PropTypes.any.isRequired,
PropTwo: PropTypes.func.isRequired,
objProp: PropTypes.Shape().isRequired
}
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Ensure a component has a single child
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| MyComponent.propTypes = {
children: PropTypes.element.isRequired
}
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Ensure a prop to be an instance of a particular class
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| MyComponent.propTypes = {
oneProp: PropTypes.instanceOf(MyClass)
}
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Full use cases from offical docs
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| import PropTypes from 'prop-types';
MyComponent.propTypes = {
// You can declare that a prop is a specific JS type. By default, these
// are all optional.
optionalArray: PropTypes.array,
optionalBool: PropTypes.bool,
optionalFunc: PropTypes.func,
optionalNumber: PropTypes.number,
optionalObject: PropTypes.object,
optionalString: PropTypes.string,
optionalSymbol: PropTypes.symbol,
// Anything that can be rendered: numbers, strings, elements or an array
// (or fragment) containing these types.
optionalNode: PropTypes.node,
// A React element.
optionalElement: PropTypes.element,
// A React element type (ie. MyComponent).
optionalElementType: PropTypes.elementType,
// You can also declare that a prop is an instance of a class. This uses
// JS's instanceof operator.
optionalMessage: PropTypes.instanceOf(Message),
// You can ensure that your prop is limited to specific values by treating
// it as an enum.
optionalEnum: PropTypes.oneOf(['News', 'Photos']),
// An object that could be one of many types
optionalUnion: PropTypes.oneOfType([
PropTypes.string,
PropTypes.number,
PropTypes.instanceOf(Message)
]),
// An array of a certain type
optionalArrayOf: PropTypes.arrayOf(PropTypes.number),
// An object with property values of a certain type
optionalObjectOf: PropTypes.objectOf(PropTypes.number),
// An object taking on a particular shape
optionalObjectWithShape: PropTypes.shape({
color: PropTypes.string,
fontSize: PropTypes.number
}),
// An object with warnings on extra properties
optionalObjectWithStrictShape: PropTypes.exact({
name: PropTypes.string,
quantity: PropTypes.number
}),
// You can chain any of the above with `isRequired` to make sure a warning
// is shown if the prop isn't provided.
requiredFunc: PropTypes.func.isRequired,
// A required value of any data type
requiredAny: PropTypes.any.isRequired,
// You can also specify a custom validator. It should return an Error
// object if the validation fails. Don't `console.warn` or throw, as this
// won't work inside `oneOfType`.
customProp: function(props, propName, componentName) {
if (!/matchme/.test(props[propName])) {
return new Error(
'Invalid prop `' + propName + '` supplied to' +
' `' + componentName + '`. Validation failed.'
);
}
},
// You can also supply a custom validator to `arrayOf` and `objectOf`.
// It should return an Error object if the validation fails. The validator
// will be called for each key in the array or object. The first two
// arguments of the validator are the array or object itself, and the
// current item's key.
customArrayProp: PropTypes.arrayOf(function(propValue, key, componentName, location, propFullName) {
if (!/matchme/.test(propValue[key])) {
return new Error(
'Invalid prop `' + propFullName + '` supplied to' +
' `' + componentName + '`. Validation failed.'
);
}
})
};
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