functionfn1(param1, param2 = 'default value') {return'return value'; } fn1('1'); JS 函数特色 no optional parameters JS 的函数没有 optional parameters 的概念, 调用的时候如果没有传入参数, 那么参数值是 undefined 传入undefined 相等于没有传入值,
In this example, the name and company parameters are both optional. If no arguments are passed to the greet function, it will use the default values for both parameters. If an object is passed to the function, it will destructure the object and use the values for name and company if they...
intsum(int a,int b)=>{int c=a+b;returnc;} (4). 命名参数(named parameters) JavaScript: ES6 中引入了参数解构的特性(parameter destructuring)。通过传入一个对象,并对其进行解构赋值来实现命名参数的特性。示例如下: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 functionsum({a,b}){returna+b...
命名空间接口空检查泛型访问修饰符Optional Parameters（可选参数）php复制代码// -- TypeScript -- //...
console.log(square(5)); // 25 function square(n) { return n * n; } 尽管square() 函数在声明之前被调用,但此代码的运行并没有任何错误。这是因为 JavaScript 解释器会将整个函数声明提升到当前作用域的顶部,因此上面的代码等价于: jsCopy to Clipboard // 所有函数声明实际上都位于作用域的顶部 functi...
RouteParameters Constructor new RouteParameters(properties) Parameter properties Object optional See the properties for a list of all the properties that may be passed into the constructor. Property Overview Any properties can be set, retrieved or listened to. See the Watch for changes topic. ...
Optional parameters are great to avoid a mess of conditional clauses at the beginning of your method. To make a parameter optional,declare its type inside of an Array, like this:{name: [String]} example: functionunique(){arguments=__({array:Array,isSorted:[Boolean],iterator:[Function]})/...
function getMapWidthHeight() { alert("Width = " + map.width + "; Height = " + map.height);} Method Details addLayer(layer, index?) Adds an Esri Layer to the map. Return type: Layer Parameters: <Layer> layer Required Layer to be added to the map. <Number> index Optional A ...
Allows trailing commas for function parameters ECMAScript 2018 Read MoreAdded rest / spread properties Added asynchronous iteration Added Promise.finally() Additions to RegExp ECMAScript 2019 Read MoreString.trimStart() String.trimEnd() Array.flat() ...
, it needs to be wired up to that event. Doing so makes that function an event handler. If you need access to the context of the invoking event, the function definition needs to include a single argument to serve as a reference to the event that fired it. This argument is ...