if(canvas.containsPoint(event, object)) { //选中该对象 canvas.setActiveObject(object); //显示菜单 showContextMenu(event, object); continue; } } //阻止系统右键菜单 event.preventDefault(); returnfalse; } //右键菜单项点击 functionshowContextMenu(event, object) { //定义右键菜单项 contextMenuItem...
functionuseRef<T>(initialValue: T): MutableRefObject<T>;//convenience overload for refs given as a ref prop as they typically start with a null value/** * `useRef` returns a mutable ref object whose `.current` property is initialized to the passed argument * (`initialValue`). The return...
UsingXORwe can type a function that returns either the data requested from an API or a response object like so: typeFetchResult<Pextendsobject>=XOR<{data:P},{error:FetchError<P>},> Now TypeScript has all the necessary information to infer ifFetchResultcontains adataor anerrorkeyat compile...
Object types in TypeScript aren't "sealed" / "closed" / "final". In other words, if you have a variable oftype{ a: string }, it's possible that the variable points to avaluelike{ a: "hello", b: 42 }. When you're directly creating an object literal, TypeScript uses "excess p...
所有通过 @typedef {object} 和@property(或者用 @prop 也可以)定义的这种类型都会被 TS 特殊解析。这里可以用 object 或Object. 你可以在 {} 中加上等号表示它具有默认值,这实际上和用方括号包裹属性名等价,但语义上看起来可能更清晰,或者在后边的属性名那里用方括号包裹加上等号——实际上这几种方式用于表示...
/*** Parses a JSON file.** @param path - Full path to the file.* @returns An object containing the JSON data.** @example Parsing a basic JSON file** # Contents of `file.json`* ```json* {* "exampleItem": "text"* }* ```** # Usage* ```ts* const result = parseFile("...
When inferring the type of an object, TypeScript will usually choose a type that’s meant to be general. For example, in this case, the inferred type ofnamesisstring[]: Copy typeHasNames = { readonly names:string[] };functiongetNamesExactly<TextendsHasNames>(arg: T): T["names"] {re...
In JavaScript, it is a runtime error to use a non-object type on the right side of the in operator. TypeScript 4.2 ensures this can be caught at design-time. Copy "foo" in 42 // ~~ // error! The right-hand side of an 'in' expression must not be a primitive. This check is...
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; }; return Foo; }()); exports.sqr = function (x) { return x * x; }; Object.defineProperty(exports, "__esModule", { value: true }); exports.default = Subscription_1.Subscription; Better IntelliSenseJavaScript IntelliSense in Visual Studio 2017 will now display a lot ...