Usage. Transpilers. At its core, optional chaining lets us write code where TypeScript can immediately stop running some expressions if we run into a null or undefined.The star of the show in optional … 如果 JavaScript 引擎不支援 optional chaining (?.) Async/await (ES2017) Object Rest/Spread Properties (ES2018) Dynamic import () (ES2020) Optional Chaining (ES2020) Nullish Coalescing (ES2020) Class Fields and Static Properties (part of stage 3 proposal) 等等！. chaining The optional chaining operator in vanilla JS | Go Make Things Babel 的作者是 FaceBook 的工程师 Sebastian McKenzie。. npm install --save-dev @babel/plugin-proposal-optional-chaining Usage With a configuration file (Recommended) { "plugins": ["@babel/plugin-proposal-optional-chaining"] } Via CLI babel --plugins @babel/plugin-proposal-optional-chaining script.js Via Node API : app.utils.clamp) There is also a proposal for a built in Math.clamp function, however, it is still in draft. Migrating from Babel – SWC Optional Chaining 1 Scope. 三、解决办法. Javascript answers related to “optional chaining undeclared variable” angular make variable optional; how to make a parameter optional in typescript; How to pass optional parameters while omitting some other optional parameters? source. false: Do not use a preset (you will need to add your own imports to the top of your entry point). Have you ever used the && operator as a fallback? obj.method?. 자바스크립트 Polyfill / Transpile / optional chaining
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