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However, if this interface is present, then the name of the intrinsic element is looked up as a property on the JSX.IntrinsicElements interface. Intrinsic elements are looked up on the special interface JSX.IntrinsicElements.īy default, if this interface is not specified, then anything goes and intrinsic elements will not be type checked. TypeScript uses the same convention that React does for distinguishing between these.Īn intrinsic element always begins with a lowercase letter, and a value-based element always begins with an uppercase letter. Intrinsic element attributes should be known intrinsically whereas components will likely want to specify their own set of attributes. The types of the attributes being passed in the JSX element should be looked up differently.For React, intrinsic elements are emitted as strings ( React.createElement("div")), whereas a component you’ve created is not ( React.createElement(M圜omponent)).a div or span in a DOM environment) or to a custom component that you’ve created. Given a JSX expression, expr may either refer to something intrinsic to the environment (e.g. In order to understand type checking with JSX, you must first understand the difference between intrinsic elements and value-based elements. tsx files, and is identical in behavior to the angle-bracket type assertion style. *Note: You can specify the JSX factory function to use when targeting react JSX emit with jsxFactory option (defaults to React.createElement) The as operator
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You can specify this mode using either the jsx command line flag or the corresponding option jsx in your tsconfig.json file. The react-native mode is the equivalent of preserve in that it keeps all JSX, but the output will instead have a. The react mode will emit React.createElement, does not need to go through a JSX transformation before use, and the output will have a. Babel).Īdditionally the output will have a. The preserve mode will keep the JSX as part of the output to be further consumed by another transform step (e.g. These modes only affect the emit stage - type checking is unaffected. TypeScript ships with three JSX modes: preserve, react, and react-native. In order to use JSX you must do two things. TypeScript supports embedding, type checking, and compiling JSX directly to JavaScript. JSX rose to popularity with the React framework, but has since seen other implementations as well. It is meant to be transformed into valid JavaScript, though the semantics of that transformation are implementation-specific.