AI代码解释 functionprocess(variable:string|number){if(typeofvariable==='string'){console.log(variable.length);// 可以访问 length 属性}else{console.log(variable.toFixed(2));// 可以调用 toFixed 方法}} 上述代码展示了如何利用typeof进行类型判断,从而在使用联合类型时实现类型保护。 类型区分 使用类型...
You can use `extends infer X` to assign the result of an expression to a variable typeSomeFunction<U>=SuperHeavyComputation<U>extendsinferResult?[Result,Result,Result]:never The trick is to use `infer X` right after the `extends` keyword...
return name.toUpperCase() } function add(numA, numB) { return numA + numB } // Shorthand const capitalize = (name) => name.toUpperCase() const add = (numA, numB) => (numA + numB) // Shorthand TypeScript (specifying variable type) const capitalize = (name: string) => name.toUpperCa...
type EventNames='click'|'scroll'|'mousemove';functionhandleEvent(ele:Element,event:EventNames){// do something}handleEvent(document.getElementById('hello'),'scroll');// 没问题handleEvent(document.getElementById('world'),'dblclick');// 报错,event 不能为 'dblclick'// index.ts(7,47): error...
off clean-up, along with arbitrary amounts of cleanup. ADisposableStackis an object that has several methods for keeping track ofDisposableobjects, and can be given functions for doing arbitrary clean-up work. We can also assign them tousingvariables because — get this —they’re also...
var global_num = 12; //global variable var Numbers = (function () { function Numbers() { this.num_val = 13; //class variable } Numbers.prototype.storeNum = function () { var local_num = 14; //local variable }; Numbers.sval = 10; //static field return Numbers; }()); console...
Even if you try to change the object structure, the compiler will point this error out. constplayerCodes={player1:9,player2:10,player3:13,player4:20};playerCodes={//Compiler Error: Cannot assign to playerCodes because it is a constant or read-onlyplayer1:9,player2:10,player3:13,player...
// Type 'string' is not assignable to type 'boolean'. } 这里使用 declare 声明了一个类型变量,然后通过类型变量里面的判定条件就能配合检查其他变量的类型了。 Any 和Unknown 的情形类似,我们还可以使用 any 来代表任意的类型,示例如下: declare function getValue(key: string): any; ...
This is the easiest solution to reason through. At the time we declare the object, go ahead and type it, and assign all the relevant values: typeOrg={name:string}constorganization:Org={name:"Logrocket"} See this in theTypeScript Playground. ...
TypeScript enforces the best practice of accessing internal fields (like id and fullName) through a reference to the class (this). Classes can also have constructor functions that include a feature C# has just adopted: automatic definition of fields. The constructor function in a TypeScript clas...